Geographical variation in Hector s dolphin: recognition of new subspecies of Cephalorhynchus hectori

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1 Journal of The Royal Society of New Zealand, Volume 32, Number 4, December 2002, pp Geographical variation in Hector s dolphin: recognition of new subspecies of Cephalorhynchus hectori Alan N. Baker 1, Adam N. H. Smith 1, and Franz B. Pichler 2 Abstract The endemic New Zealand dolphin Cephalorhynchus hectori has been shown through genetic analyses to consist of four regional populations separated to various degrees both geographically and reproductively. A morphological study of skull and mandible features was undertaken to examine variation between the most genetically distinct population, occurring on the west coast of the North Island, and the populations around the South Island. Univariate and principal component analyses demonstrate that the North Island population can be differentiated from the southern populations on the basis of several skeletal characters. These characters, plus the genetic evidence of haplotype differences and absence of gene-flow between populations, enable us to formally describe the North Island population of Hector s dolphin as a new subspecies, C. hectori maui, and the nominate South Island populations as C. hectori hectori. Keywords Cetacea; Delphinidae; Cephalorhynchus; taxonomy; genetics; subspecies; New Zealand INTRODUCTION Hector s dolphin (Cephalorhynchus hectori Van Bénéden 1881) is endemic to New Zealand waters, where it lives close to the shore around the South Island and on the west coast of the North Island (Fig. 1). Genetic analyses of the mitochondrial (mt) DNA population structure of Hector s dolphins have identified four regional populations, connected by little or no female migration (Pichler 2002). The smallest population (c individuals) lives on the north-west coast of the North Island between Mokau (38 40 S) and Kaipara Harbour (36 30 S) (Russell 1999), and is genetically distinct from the other, southern populations. The North Island population of Hector s dolphins has declined over recent historic time, coincident with the advent of coastal set-net fishing (Russell 1999; Dawson et al. 2001). The population is currently regarded to be not only declining, but contracting in range, and its future survival is threatened (Martien et al. 1999; Pichler & Baker 2000; Dawson et al. 2001; Pichler 2002). The discovery that the North Island population of Hector s dolphins is genetically distinct from those around the South Island has raised the question of its taxonomic status. If the isolation and genetic difference is such that it cannot effectively breed with the southern populations, and if it shows consistent and diagnosable morphological differences from those populations, it should be considered a distinct cetacean taxon. 1 Science and Research Unit, Department of Conservation, P.O. Box , Wellington, New Zealand. 2 School of Biological Sciences, University of Auckland, Private Bag , Auckland, New Zealand. R02026 Received 15 July 2002; accepted 26 August 2002; published 26 November 2002

2 714 Journal of The Royal Society of New Zealand, Volume 32, 2002 Fig. 1 New Zealand place names mentioned in the text and current distribution of the four regional populations of Hector s dolphins (thick coastal lines).

3 Baker et al. Subspecies of Hector s dolphin 715 Geographic variation in morphological features is one tool for delimiting marine mammal populations as separate taxa, and the strongest differentiation tends to develop between populations which are both geographically and reproductively isolated (Mayr & Ashlock 1991). In the case of Hector s dolphins, that isolation has been shown to exist through demographic (Bräger 1999) and phylogenetic (Pichler 2002 and references therein) analyses. Modern species or subspecies classification is primarily a question of concordance between the results of phylogenetic analyses, morphology-based taxonomy, and biogeography; therefore, to elucidate the taxonomic status of the North Island population a study of the variation in morphological features has been undertaken. This paper gives the results of multivariate statistical analyses of skull and mandible features of 59 specimens of Hector s dolphin, which, taken together with the known genetic differentiation, confirm the distinctness of the North Island population and provide strong evidence for its classification as a new subspecies of Cephalorhynchus hectori. An earlier described subspecies, C. hectori bicolor Oliver (1946) has been invalidated by van Bree (1972) on the basis that the description was made without an actual specimen (e.g., no type specimen), and the subspecies was not diagnosed and compared with the nominate form (i.e., the orginal description of C. hectori). Oliver s (1946) description was based entirely on his field observations of a pale external colour of Marlborough Sounds and Cloudy Bay specimens, which he believed was different from the common C. hectori, despite an earlier indication that he understood there was some variation in the colour of this species (Oliver 1922; also see Baker 1973). We agree that the description of bicolor is insufficient to attribute it to any one of the currently known populations of C. hectori. MATERIALS AND METHODS Material and data collection Skeletal material of Hector s dolphins was examined in the Taranaki Museum, New Plymouth (TM); Whanganui Regional Museum, Wanganui (WRM); and Museum of New Zealand Te Papa Tongarewa, Wellington (NMNZ). The material originated from by-catch and beachcast specimens. The data set used in analysis contains 59 adult individuals, 46 from the South Island and 13 from the North Island. Three museum specimens attributed to the North Island in Pichler (2002) require comment: one, a skull and parts of a post-cranial skeleton, of definite North Island provenance from Oakura, Taranaki (TM A57.705), showed up as a significant outlier in the analysis, with its skull characters nesting completely within parameters for South Island material. DNA sequences from this specimen showed it possessed a rare N haplotype, known only from one other specimen, from Kaikoura on the north-east coast of the South Island (Pichler 2002). The Oakura specimen has been excluded from the analysis because there is a strong possibility that it represents an individual that has crossed Cook Strait from the south, alive or dead. The specimen was found in an advanced state of decomposition with parts of the vertebral column, teeth, and lower jaws missing, which indicated it may have been floating dead before being washed ashore. A second specimen (NMNZ 1615) from Waikanae Beach, on the northern side of Cook Strait, was found to possess the common west coast South Island J haplotype, and is excluded from the analysis for the same reason as the Oakura specimen. A third skull, allegedly from the Bay of Islands in the far north of the North Island (NMNZ 274), also had the J haplotype. Research into the NMNZ specimen registers has shown that the first entry for this specimen in the late 1870s was without locality or collector data. It was not until Oliver (1922) published a review of the New Zealand Cetacea that the specimen was

4 716 Journal of The Royal Society of New Zealand, Volume 32, 2002 listed as coming from the Bay of Islands, but without any supporting information. During the period , the museum s then director, Sir James Hector, was actively recording and describing New Zealand cetaceans (including the first discovery and assignment of Hector s dolphins to Lagenorhynchus clanculus Gray (Hector 1872)), and we contend that if a specimen of this dolphin had arrived at the museum from the geographically remote and then largely biologically unexplored far north of New Zealand, he would have recorded it in one of his papers, or at least recorded it correctly in the museum register. The uncertain provenance of this specimen, together with the morphological and genetic data suggesting a southern origin, requires us to exclude it from the analysis. Table 1 Means, sample sizes, and ranges for skull and mandible measurements from North and South Island Hector s dolphins, with mean and standard error (SE) of the difference and P-values from an independent-samples t-test. Although the P-values are not particularly meaningful when they are this small, they are displayed here as a relative index of difference between the two populations. Acronyms for the measurements (all in mm) are to be translated as follows: CBL = condylobasal length; RL = rostrum length; RW = rostrum width (at base); RW1/2 = rostrum width (at half length); RW3/4 = rostrum width (at 3/4 length); PW = premaxillae width (at half rostrum); TREN = tip rostrum to right external nare; TRIN = tip rostrum to internal nares; WPR = width preorbital process; WPO = width across postorbital processes; ZW = zygomatic width; WPRM = maximum width of premaxillae; PB = maximum parietal breadth; EHB = external height braincase; ILB = internal length braincase; LTF = maximum length left temporal fossa; WTF = maximum width left temporal fossa; LO = length left orbit; WIN = maximum width internal nares; LRAM = maximum length left ramus of mandible; HRAM = maximum height left ramus; LLTRL = length lower tooth row left; LLTRR = length lower tooth row right; LUTRL = length upper tooth row left; LUTRR = length upper tooth row right. North Island South Island Difference Measure Mean N Range Mean N Range Mean SE P CBL RL RW RW1/ RW3/ PW TREN TRIN WPR WPO ZW WPRM PB EHB ILB LTF WTF LO WIN LRAM HRAM LLTRL LLTRR LUTRL LUTRR

5 Baker et al. Subspecies of Hector s dolphin 717 Where possible, 40 skull and mandibular measurements were taken according to procedures described in Perrin (1975). A selection of the measurements which show significant geographical variation is listed in Table 1. Fifteen post-cranial skeletal measurements were recorded for some of the specimens but these variables were limited in availability and are therefore not included in the analysis. No obviously juvenile specimens were used in this study, and the degree of physical maturity in the subadult and adult specimens measured was estimated by the amount of fusion of cranial sutures, particularly in the parieto-occipital suture system, and the amount of vertebral disc fusion, following Perrin (1975). Samples used here would equate to Perrin s Class IV and higher (i.e., specimens ranging from those with no vertebral epiphyses fused to full fusion, and with some or complete fusion of the zygomatic-parietal/exoccipital, parietobasioccipital, and frontal-supraoccipital sutures). Examination revealed that over the range of physical maturity recorded, that factor had no apparent effect on the measurements for the series of subadults and adults available. Gender information was available for 34 of the 59 specimens: in the South Island sample, 14 were female and 11 were male; in the North Island sample there were 2 females and 8 males. We tested for significant differences between the sexes within the larger and genderbalanced South Island sample to see if this difference in gender ratio would influence our between-population comparisons. For most of the South Island specimens it was possible to further identify these as originating from the east coast or west coast South Island subpopulations. We decided, however, to carry out most of the analyses using a North Island or South Island designation. This is because we are more interested in this comparison, the information is more complete and reliable, and there is little or no morphological difference between the regional populations of the South Island. Diagnosability According to Patten & Unitt (2002), to diagnosably distinguish a new subspecies from its current taxon we must demonstrate not only mean differences for some variable, but a large degree of separation of the distributions. The generally accepted criterion is for 75% of a population to lie beyond 99% of the other on some variable (Rice 1998). To conclusively diagnose a new subspecies, one must demonstrate this separation for each of the two populations from the other. The population distributions are estimated from the sample parameters by using the t-distribution. The test can be applied to individual variables or to two or more variables combined using multivariate data reduction techniques or discriminant analysis. Where Population 2 has the largest mean, Patten & Unitt (2002) give the formula D = µx 2 S 2 (t 0.25,df2 ) µx 1 S 1 (t 0.01,df1 ) where: D i is the index of separation for population i, µx is the sample mean for population i, S i is the sample standard deviation for population i, t P,df is the critical value calculated from the Student s t-distribution with P probability (in this case 0.25 and 0.01) and df, degrees of freedom. This provides us with the test statistic, D, which can be used to determine whether the 75% separation criterion is met. If D 0, then Population 2 is diagnosably distinct from Population 1. To determine if Population 1 is distinct from Population 2, the same test is performed after swapping the P-values when computing the critical t-value. One can also use this formula to estimate the percentage separation of the populations, that is, how much of one population lies beyond the range of the other, instead of testing only for 75% separation. This is done by

6 718 Journal of The Royal Society of New Zealand, Volume 32, 2002 altering the appropriate P-value when calculating the t-statistic and finding the point when the D-value becomes positive. These percentages are highly dependent on the sample size and standard deviation, and should be viewed as the minimum percentage separation that can be validated by the sample. Data analysis Using the computer program SPSS for all morphological analyses, we examined the skull and mandible variables individually and tested them for significance using independent samples t-tests. Those variables without missing data which gave the most significant differences were then put into a stepwise discriminant function analysis. The order in which this analysis chose the variables enabled us to determine the variables order of importance in discriminating between the North and South Island dolphins, while taking into account correlation between the variables. The best discriminating variables were examined individually using boxplots and in pairs using scatterplots. We took the best discriminating variables, derived the D-values and tested for 75% separation as described by Patten & Unitt (2002), and estimated the percentage separation between the populations. Principal component analysis (PCA) is a well-known multivariate technique which reduces the information of many variables into fewer, orthogonal dimensions. These principal components (PCs) are created so that they account for the maximum amount of variance possible and are a useful tool for finding the source of variation in the data. An important aspect of PCA, as opposed to discriminant analysis, is that it does not use any information on group membership and, thus, only accounts for the variation observed in the data. Various PCs were investigated and the percentatge separation was estimated. RESULTS Skull and mandible morphology The significance levels from a 2-tailed independent-samples t-test, as shown in Table 1, confirm that the North Island Hector s dolphin skulls are undoubtedly larger than those of South Island populations in many dimensions. However, mean differences alone are not sufficient to support the allocation of a population to a new taxon. To do this we need to show that the distributions of some variable (or combination of variables) are not only different, but that a significant proportion of one population, usually 75%, are beyond the range of the other (Patten & Unitt 2002). The measurement that best distinguishes the North Island population from the South is rostrum width at half length, as apparent from the P-value of the mean difference and that it was selected first in the stepwise discriminant function analysis (DFA). There is, in fact, no overlap between the North and South Island samples for this variable. The second variable selected by the stepwise DFA was rostrum length, suggesting that the overall size of the rostrum is the most important diagnostic feature. Fig. 2 illustrates this size difference and shows that rostrum width at half length completely separates our samples of North and South Island Hector s dolphins. Other important variables also show differences between the populations (Fig. 3). Boxplots are particularly useful to this study because they so clearly illustrate the 75% separation rule. The markers on the graph represent our points of interest. The box edges represent quartiles and, therefore, 75% of the sample is to the right of the left-most box edge, and vice versa. The hairs represent the maximum and minimum of the sample. If the hair from Sample 1 does not overlap with the closest box edge of Sample 2, then 75% of Sample 2 is beyond the range of Sample 1. These graphs, however, only show the samples and not the

7 Baker et al. Subspecies of Hector s dolphin 719 Fig. 2 Rostrum length and width at half length in the three regional populations of Hector s dolphins. Ø, individual from the South Island west coast population; ı, South Island east coast population; Ç, South Island population, region unknown; +, North Island west coast population. populations. It is the underlying distribution of the variable, which is estimated using the sample, that is used to calculate the D-statistic and percentage separation. Thus, the principal diagnostic characteristics of North Island Hector s dolphin skulls are rostrum length and width at half rostrum length. The rostrum is longer and wider in the North Island specimens than in the South Island specimens. Group prediction based on a discriminant analysis on these two variables classified 100% of the sample to the correct island. The two populations are estimated to be at least 84% separable from each other on the basis of rostrum width at half length, which is to say that 84% of each population, as estimated from the sample using the t-distribution, is beyond the range of the other. Other skull and mandibular measurements, such as length of upper and lower tooth rows, width of premaxillae at mid-rostrum and length of rostrum to external nares, reflect similar patterns to those shown in Fig. 3. We used PCA to combine a set of variables that did not include dimensions of the rostrum to see what separation existed in the remaining measurements. The variables entered were condylobasal length, zygomatic width, maximum width of premaxillae, and maximum length of left ramus of mandible. The first PC accounts for 86% of the variation in the data (Fig. 3). It is apparent from this that the majority of the variation in the data is due to the difference between the populations. Despite the obvious separation that this variable shows, it did not meet the 75% criterion. On the first PC, 73% of the North Island population is separable from the South and 64% of the South Islanders are separable from the North. Note, however, that the D-statistic which tests for separation is highly dependent on a low standard deviation and PCs have an inherently high variation.

8 720 Journal of The Royal Society of New Zealand, Volume 32, 2002 There was potential in the samples for the identification of sexual dimorphism, with an associated problem of a much higher proportion of males than females in the North Island sample. Investigation of the larger South Island sample revealed that the females had a slightly higher mean than the males for most of the skull measurements. This difference was significant in only 2 of the 40 measurements for a 2-tailed independent-samples t-test (width of premaxillae, df = 45, P = 0.011; length of left orbit, df = 42, P = 0.033), and this can be expected from chance alone when 40 t-tests are performed. We therefore found no significant evidence for sexual dimorphism in the skulls of Hector s dolphins. However, we considered the effect of the possible sexual dimorphism on our conclusion that North Island skulls are larger than those of the South Island populations. The unlikely event that there is sexual dimorphism in skulls in favour of females would only strengthen our overall conclusion about larger North Island skulls, because of the much higher proportion of males in the North Island sample. Other morphological differences Total body length Russell (1999) reported that adult North Island Hector s dolphins range in length from 120 to 162 cm. She compared the total body length of 27 North Island specimens with data from South Island specimens and, using the Mann-Whitney U-test, found significant differences between them, for both sexes: U = 98.5, n 1 = 13, n 2 = 8, P < between females, and U = 123, n 1 = 24, n 2 = 8, P < 0.01 between males. Both sexes of North Island dolphins are significantly longer that those from the South Island. Colour pattern Hector s dolphins have a sexually dimorphic colour pattern in the region around the genital slit (Slooten & Dawson 1988). In males from the South Island, there is an elongated heartshaped black patch around the penial slit, which is narrow and pointed anteriorly, and rounded, with a medial depression posteriorly. No fresh North Island specimens were available to us for study, but photographs of three recently dead male specimens showed that NMNZ 2607 and 2609 each had a very reduced or no genital patch, and NMNZ 2608 had a patch with a white centre and narrow, dark margins anteriorly, markedly different from the all-black South Island patch. This colour difference needs to be further investigated, and it is possible that other aspects of the relatively complex colour pattern of Hector s dolphin will show regional variations. DISCUSSION We have shown that the North Island population of Hector s dolphins differs morphologically from the South Island populations, but is this differentiation, together with the known genetic differences, sufficient to rank the northern population as a separate species or subspecies? According to the traditional Morphological Species Concept (Mayr 1982), the criterion of species status is the degree of phenotypic difference: a species is distinguished from all others by differences in its morphology. Reproductive isolation, as promoted in the Biological Species Concept (see Mayr 2000), has also been regarded as an important species criterion. Despite reservations about the relevance of reproductive isolation to speciation, especially for allopatric populations (Martin 1996), Avise & Ball (1990) and Avise (2000) suggest that the category species should continue to refer, in principle, to reproductively isolated units (i.e., those without inter-unit gene flow).

9 Baker et al. Subspecies of Hector s dolphin 721 Fig. 3 Distributions of five measurements and principal component 1 (see text) for the North and South Island populations, demonstrating the clear morphological separation between them. A, Rostrum width at half length; B, rostrum length; C, zygomatic width; D, condylobasal length; E, length of ramus of left mandible; F, principal component 1. Scale axes for plots A E are in millimetres. Circles on the plots represent outliers.

10 722 Journal of The Royal Society of New Zealand, Volume 32, 2002 Whereas the North Island Hector s dolphin specimens have shown some distinct morphological characters (e.g., long and wide rostrum), and the genetic evidence (see below) is that the population is both reproductively and genetically isolated, the characters which distinguish this population from the others are not, in our view, consistent with skeletal characters used to separate other cetacean species (e.g., Lagenorhynchus spp. (Fraser 1966) and Stenella spp. (Perrin 1975)). The differentiating skull characters are, however, of a similar nature to those used by Perrin (1990) in his description of three subspecies of Stenella. Avise (2000) recommended that subspecies should conform to evolutionary significant units (ESU), i.e., one or a set of conspecific populations with a distinct, long-term evolutionary history, mostly separate from other such units. Dizon et al. (1994) characterised populations with the highest probability of being an ESU as having a discontinuous genetic divergence pattern where a locally adapted and closely related population is geographically separated; this increases the probability that habitat differences exist between isolated populations, resulting in different selection pressures. The North Island population of Hector s dolphins fits this ESU definition, despite apparently not having a long-term evolutionary history, and therefore meets that particular criterion for subspecific status. Molecular information from gene sequences can provide supporting evidence for taxonomic recognition of cetaceans (Dizon et al. 1991; Dalebout et al. 1998). Pichler et al. (1998) and Pichler (2002) showed that multidimensional scaling of genetic differences among the local populations of Hector s dolphins reveals four clusters consistent with a four-regional pattern (west coast North Island, east coast South Island, west coast South Island, and south coast South Island (Fig. 4). Pichler (2002) demonstrated that the local populations within regions are connected by gene flow only with immediately adjacent populations (fitting a 1-dimensional stepping stone model), while the relationships of subpopulations between regions are more consistent with a complete isolation model, equivalent to geographic barriers. The sharp distinction between mtdna haplotypes across these populations suggested that there is little female interchange, leading Pichler et al. (1998) to categorise them as genetic management units, i.e., populations that are genetically distinct and demographically independent. A preliminary analysis of microsatellite variation also detected significant differentiation between three of the four regional populations (east coast and west coast South Island, and west coast North Island) (Pichler 2002). In the North Island population, the fixation of a unique mtdna haplotype and near fixation of rare or unique microsatellite alleles suggests that it is reproductively isolated from the two South Island populations (Pichler 2002). Pichler & Baker (2000) found that Hector s dolphin populations have a low genetic diversity similar to that seen in other odontocete cetaceans with low abundance. The North Island population had the lowest haplotype diversity (0.197) and nucleotide diversity (0.136%) of the four regional populations. Furthermore, the only mtdna variation in the North Island was found in museum specimens (see Material and data analysis, above) while all contemporary specimens share a single unique haplotype (a G type) (Pichler et al. 2001; Pichler 2002). The low contemporary diversity of the North Island population is likely to have resulted from a recent decline in abundance due to incidental mortality. However, the historic diversity was also low, suggesting that the North Island population may never have been large. A small original population on the north-west coast of New Zealand may be because the north-west coast of the North Island is washed by a southward-flowing branch of the warm, tropicaloriginating East Australian Current, possibly providing less than optimal conditions for C. hectori in that area. The southern populations live in coastal waters influenced by the cooler, northwards-flowing Southland and Westland currents.

11 Baker et al. Subspecies of Hector s dolphin 723 Fig. 4 Multidimensional scaling plot of genetic distance (d A ) to show the relative genetic distance separating the four populations of Hector s dolphins (after Pichler 2002). The nature of the isolating mechanism which has restricted the North Island population to the coastal area north of Cook Strait is worthy of comment: the distribution of Hector s dolphins has been extensively studied in recent years, especially around the South Island (Dawson & Slooten 1988). The northern population is believed to have once ranged much of the west coast of the North Island between northern Cook Strait (41 S) and Ninety Mile Beach (34 45 S) (Russell 1999). Recent surveys along the North Island s west coast by Dawson & Slooten (1988), Russell (1999), and S. Ferreira and C. Roberts (pers. comm., based on a Department of Conservation aerial survey in ) have shown that the population has become restricted to a small part of its range between North Taranaki (38 40 S) and Kaipara Harbour (36 25 S), making it even further isolated from the southern populations. The original isolation of the North Island Hector s dolphin population from the east coast of the South Island can be attributed to a continuous shoreline of New Zealand before the mid Pleistocene, and a later separation of the North and South Islands by the opening of Cook Strait during late Pleistocene and Holocene interglacial periods (Stevens 1980; Lewis et al. 1994; Pichler 2002). During the Pliocene and early Pleistocene, the west coast South Island and west coast North Island populations would have been contiguous, but separated from the east coast South Island population. The west coast population may have fragmented latitudinally, with a northern group eventually separating off from those further south. Being a depth-limited species, the northern group would have become trapped in the waters of the North Island by the later opening of Cook Strait. Short-range population fragmentation may be due to natal fidelity, resulting in population differentiation even along contiguous coastlines, such as during a glacial period (Pichler & Baker 2000). Further isolation between local populations can also be a result of ecological preference and strong philopatry (Dawson & Slooten 1993). Therefore, the small home range (<60 km) and residential nature of Hector s dolphins (Baker 1983; Bräger 1999) has contributed to its isolation, and, consequently, the reduced genetic diversity, by imposing a limit on dispersal.

12 724 Journal of The Royal Society of New Zealand, Volume 32, 2002 Assessments of speciation durations from mtdna studies have shown that median evolutionary time associated with sequence divergence (i.e., the speciation process) between polygroups or sister species of mammals is c. 2.2 million years (Avise et al. 1998; Avise 2000). An estimate of the time at which the North Island population of Hector s dolphins was effectively separated from the South Island is yr BP, based on the last postglacial opening of Cook Strait (Pichler et al. 2001). Although the above estimates of the duration of mammalian speciation are subject to wide variation, the time scale involved in the differentiation of the North Island Hector s dolphin is probably too short for a full species to develop. Overall, when all lines of evidence are taken into account, we believe the population must be ranked as a subspecies of C. hectori. CONCLUSION North Island Hector s dolphins are a morphologically and genetically distinct allopatric population. Mayr & Ashlock (1991) considered it preferable to treat allopatric populations of doubtful rank as subspecies, because the use of trinomial nomenclature conveys two important pieces of information, the closest relationships and allopatry. The current genetic and morphological evidence indicates that the North Island population of Hector s dolphins are in the process of speciation but have not yet reached full specific status. If further analysis shows specific status is warranted, the subspecies can then be elevated to full species level. We therefore designate the North Island population as the subspecies Cephalorhynchus hectori maui. All South Island populations are here referred to the nominate form, C. hectori hectori. TAXONOMIC TREATMENT Class Cetacea Family Delphinidae Genus Cephalorhynchus Gray 1846 Cephalorhynchus hectori hectori (Van Bénéden 1881) new subspecies Full synonymy for the species is given in Baker (1978). This subspecies includes all populations of Hector s dolphins living in the coastal waters of New Zealand s South Island. HOLOTYPE: Post-cranial skeleton in the Louvain Museum, Belgium (P. J. H. van Bree pers. comm. 20 October 1986). Specimens examined in this study referred to C. hectori hectori: NMNZ 555, 1677, 1730, 1913, 1915, 1960, 2001, 2002, 2004, 2005, 2006, 2007, 2010, 2011, 2015, 2019, 2020, 2021, 2022, 2025, 2026, 2052, 2057, 2058, 2061, 2062, 2068, 2070, 2071, 2072, 2125, 2169, 2224, 2277, 2278, 2279, 2281, 2282, 2286, 2287, 2288, 2289, 2290, 2291, 2294, DIAGNOSIS: Morphological: relatively small adult skull (condylobasal length mm, zygomatic width mm), relatively small adult rostrum (length mm, width at half length mm), total body length to at least 1530 mm for females and 1440 mm for males. MOLECULAR: Mitochondrial DNA: 16 haplotypes (n = 251); haplotype diversity h = 0.789, = 0.715%; three isolated subpopulations (east coast, west coast, south coast). Diversity reduced in present-day east coast subpopulation. Microsatellite allele size ranges: 409/470 = , EV1 = , EV14 = , EV37 = , EV104 = DISTRIBUTION: Tasman Bay, Marlborough Sounds, east coast of South Island, south coast of South Island, and west coast of South Island, excluding Fiordland. Note that Van Bénéden s

13 Baker et al. Subspecies of Hector s dolphin 725 (1881) type of Electra hectori was said to have come from the north-eastern coast of New Zealand. It is most unlikely, however, that this specimen came from the north-eastern coast of the North Island, as no other specimen has since been positively identified from that region. It is more likely that the specimen came from the north-eastern coast of the South Island, where it is relatively common. Van Bénéden s specimen was a juvenile 105 cm total body length. Cephalorhynchus hectori maui new subspecies The population of Hector s dolphins living in the coastal waters of the north-west coast of New Zealand s North Island. HOLOTYPE: NMNZ 2607, skull, mandibles and disarticulated post-cranial skeleton, Karioitahi Beach, Waiuku, North Island, New Zealand ( S, E), 20 Jan 2002, collected by Simon Mowbray, Department of Conservation, male, 1390 mm total length, condylobasal (CBL) 310 mm, vertebral count 7 cervical, 12 thoracic, 17 lumbar, 28 caudal. PARATYPES: NMNZ 275, 1734, 2410, 2608, 2609; TM A57.764, A71.765, A71.766, A78.570, A78.575, A78.620; WRM NH070. ETYMOLOGY: In a Maori legend about the creation of Aotearoa/New Zealand, Maui is a hero (male gender) who fished up the North Island, Te Ika a Maui, from the ocean depths. The common name of this subspecies will be Maui s dolphin. DIAGNOSIS: Morphological: relatively large adult skull (CBL 284 to at least 319 mm, zygomatic width of 148 to at least 167 mm), relatively large adult rostrum (length 143 to at least 165 mm, width at half length 57 to at least 64 mm), total body length to at least 1625 mm for females, and 1460 mm for males. MOLECULAR: Mitochondrial DNA: 3 haplotypes (n = 29); haplotype diversity h = 0.197, = 0.136%; The North Island is fixed for a single unique mtdna haplotype G in the presentday samples. Microsatellite allele size ranges: 409/470 = ( 188 is unique to North Island), 415/416 = ( 218 is unique to North Island), EV1 = , EV14 = 149, EV37 = 182, EV104 = 158; microsatellite heterozygosity is low for the three variable loci (0.250, 0.143, and 0.083, respectively). DISTRIBUTION: North-west coast of the North Island of New Zealand, between Taranaki and Ninety Mile Beach. ACKNOWLEDGMENTS We thank Ian Westbrooke, Department of Conservation, Michael Ryan, Statistics New Zealand, and Jennifer Brown, Department of Mathematics and Statistics, University of Canterbury, for advice and assistance with the statistical analyses. Ron Lambert and Amanda Ward (TM), Patricia Nugent (WRM), and Anton van Helden (NMNZ) kindly arranged access to the Hector s dolphin collections in their institutions. Many of the NMNZ specimens were orginally provided by Elisabeth Slooten and Stephen Dawson, Department of Marine Science, University of Otago. Nadine Gibbs, and Pádraig Duignan, Institute of Veterinary, Animal, and Biomedical Research, Massey University, and Anton van Helden assisted with the preparation of specimens for study. Jim Lilley of J. Lilley and Associates, Christchurch, provided photographs of Hector s dolphins from their database. Peter van Bree, Zoological Museum, Amsterdam, provided information on the whereabouts of the type specimen of C. hectori, and Geoffrey Chambers, School of Biological Sciences, Victoria University, Koen Van Waerebeek, Peruvian Centre for Cetacean Research, Lima, Frank Cipriano, State University of San Francisco, and two referees, made valuable comments on the manuscript. The Marsden Fund, administered by the Royal Society of New Zealand, supported the genetic analysis. We thank field staff of the Department of Conservation for the important work they do in attending marine mammal strandings and collecting biological data and samples.

14 726 Journal of The Royal Society of New Zealand, Volume 32, 2002 REFERENCES Avise, J. C. 2000: Phylogeography: the history and formation of species. London, Harvard University Press. 447 p. Avise, J. C.; Ball, R. M. Jr. 1990: Principles of genealogical concordance in species concepts and biological taxonomy. Oxford Surveys in Evolutionary Biology 7: Avise, J. C.; Walker, D.; Johns, G. C. 1998: Speciation durations and Pleistocene effects on vertebrate phylogeography. Proceedings of the Royal Society of London B 265: Baker, A. N. 1973: Introduction to notes on Hector s dolphin, Cephalorhynchus hectori (Van Bénéden) from New Zealand. Records of the Dominion Museum 8(9): Baker, A. N. 1978: The status of Hector s dolphin, Cephalorhynchus hectori (Van Beneden) in New Zealand waters. Report of the International Whaling Commission 28: Baker, A. N. 1983: Whales and dolphins of New Zealand & Australia: an identification guide. Wellington, Victoria University Press. 133 p. Beneden, P.-J. Van 1881: Notice sur un nouveau dauphin de la Nouvelle-Zélande. Bulletin Academe Royale de Belgique (3)1: Bräger, S. 1999: Association patterns in three populations of Hector s dolphin, Cephalorhynchus hectori. Canadian Journal of Zoology 77: Bree, P. H. J. van 1972: On the validity of the subspecies Cephalorhynchus hectori bicolor Oliver, Investigations on Cetacea 4: Dalebout, M. L.; van Helden, A. L.; Van Waerebeek, K.; Baker, C. S. 1998: Molecular genetic identification of southern hemisphere beaked whales (Cetacea: Ziphiidae) Molecular Ecology 7: Dawson, S. M.; Slooten, E. 1988: Hector s dolphin Cephalorhynchus hectori: distribution and abundance. Reports of the International Whaling Commission Special Issue 9: Dawson, S. M.; Slooten, E. 1993: Conservation of Hector s dolphins: the case and process which led to establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation 3: Dawson, S.; Pichler, F.; Slooten, E.; Russell, K.; Baker, C. S. 2001: The North Island Hector s dolphin is vulnerable to extinction. Marine Mammal Science 17: Dizon, A. E.; Southern, Ŝ. O.; Perrin, W. F. 1991: Molecular analysis of mtdna types in exploited populations of spinner dolphins (Stenella longirostris). Reports of the International Whaling Commission Special Issue 13: Dizon, A. E.; Perrin, W. F.; Akin, P. A. 1994: Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern tropical Pacific: a phylogeographic classification. NOAA Technical Report National Marine Fisheries Service p. Fraser, F. C. 1966: Comments on the Delphinoidea. In: Norris, K. S. ed. Whales, dolphins and porpoises. Berkeley and Los Angeles, University of California Press. Pp Hector, J. 1872: On the new Zealand bottlenose (Lagenorhynchus clanculus Gray). Annals and Magazine of Natural History (IV)9: Lewis, K. B.; Carter, L.; Davey, F. J. 1994: The opening of Cook Strait: interglacial tidal scour and aligning basins at a subduction to transform plate edge. Marine Geology 116: Martien, K. K.; Taylor, B. L.; Slooten, E.; Dawson, S. 1999: A sensitivity analysis to guide research and management for hector s dolphin. Biological Conservation 90: Martin, G. 1996: Birds in double trouble. Nature 380: Mayr, E. 1982: The growth of biological thought: diversity, evolution, and inheritance. Cambridge, Belknap Press. Mayr, E. 2000: The biological species concept. In: Wheeler, Q.; Meier, R. ed. Species concepts and phylogenetic theory. New York, Columbia University Press. Pp Mayr, E.; Ashlock, P. D. 1991: Principles of systematic zoology. 2nd ed. New York, McGraw-Hill. Oliver, W. R. B. 1922: A review of the Cetacea of the New Zealand seas. Proceedings of the Zoological Society of London 3: Oliver, W. R. B. 1946: A pied variety of the coastal porpoise. Dominion Museum Records in Zoology (1)1: 1 4. Patten, M. A.; Unitt P. 2002: Diagnosability versus mean differences of Sage sparrow subspecies. The Auk 119(1): Perrin, W. F. 1975: Variation of the spotted and spinner porpoise (Genus Stenella) in the eastern Pacific and Hawaii. Bulletin of the Scripps Institution of Oceanography 21: Perrin, W. F. 1990: Subspecies of Stenella longirostris (Mammalia: Cetacea: Delphinidae). Proceedings of the Biological Society of Washington 103(2):

15 Baker et al. Subspecies of Hector s dolphin 727 Pichler, F. 2002: Genetic assessment of population boundaries and gene exchange in Hector s dolphin. Department of Conservation Science Internal Series p. Pichler, F.; Baker, C. S. 2000: Loss of genetic diversity in the endemic Hector s dolphin due to fisheries-related mortality. Proceedings of the Royal Society of London, Series B 267: Pichler, F.; Dawson, S. M.; Slooten, E.; Baker, C. S. 1998: Geographic isolation of Hector s dolphin populations described by mitochondrial DNA sequences. Conservation Biology 12: Pichler, F.; Robineau, D.; Goodall, R. N. P.; Meyer, M. A.; Olavarría, C.; Baker, C. S. 2001: Origin and radiation of the genus Cephalorhynchus. Molecular Ecology 10: Rice, D. W. 1998: Marine mammals of the world systematics and distribution. Society for Marine Mammalogy Special Publication p. Russell, K. 1999: The North Island Hector s dolphin: a species in need of conservation. Unpublished MSc thesis, University of Auckland, Auckland, New Zealand. 136 p. Slooten, E.; Dawson, S. M.1988: Studies on Hector s dolphin, Cephalorhynchus hectori: a progress report. Reports of the International Whaling Commission Special Issue 9: Stevens, G. R. 1980: New Zealand adrift. The theory of continental drift in a New Zealand setting. Wellington, A. H. & A. W. Reed. 442 p.

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