Comparative phylogeography of coastal limpets across a marine disjunction in New Zealand

Cook Strait, which separates the North and South Island of New Zealand, has been a transient, but re-occurring feature of the New Zealand land mass throughout the Pleistocene, maintaining its current width and depth for the past 5000 years. Historic land fragmentation coupled with the complex hydrography of the Greater Cook Strait region has created both biogeographic and phylogeographic disjunctions between the North and South Island in several marine species. Here we use mitochondrial cytochrome b DNA sequences of three endemic intertidal limpets, Cellana ornata, Cellana radians and Cellana flava to assess intraspecific phylogeographic patterns across Cook Strait and to look for interspecific concordance of ecological and evolutionary processes among closely related taxa. We sequenced 328-359 bp in 85-321 individuals from 8-31 populations spanning the biogeographic range of the three species. Intraspecific phylogeographic analyses show moderate to strong genetic discontinuity among North and South Island populations due to allopatric fragmentation. This pattern was broadly concordant across the three species and the observed divergence among this group of intertidal limpets (0.3-2.0%) is similar to that of previously studied subtidal organisms. For each species, divergence time calculations suggest contemporary North and South Island lineages diverged from their respective most recent common ancestor approximately 200 000 to 300 000 years before present (bp), significantly earlier than previous estimates in other coastal marine taxa that arose from a miscalculation of divergence time.     

Glacial refugia in a maritime temperate climate: Cicada (Kikihia subalpina) mtDNA phylogeography in New Zealand

Understanding the biological significance of Pleistocene glaciations requires knowledge of the nature and extent of habitat refugia during glacial maxima. An opportunity to examine evidence of glacial forest refugia in a maritime, Southern Hemisphere setting is found in New Zealand, where the extent of Pleistocene forests remains controversial. We used the mitochondrial phylogeography of a forest-edge cicada ( Kikihia subalpina ) to test the hypothesis that populations of this species survived throughout South Island during the Last Glacial Maximum. We also compared mitochondrial DNA phylogeographic patterns with male song patterns that suggest allopatric divergence across Cook Strait. Cytochrome oxidase I and II sequences were analyzed using network analysis, maximum-likelihood phylogenetic estimation, Bayesian dating and Bayesian skyline plots. K. subalpina haplotypes from North Island and South Island form monophyletic clades that are concordant with song patterns. Song divergence corresponds to approximately 2% genetic divergence, and Bayesian dating suggests that the North Island and South Island population-lineages became isolated around 761 000 years bp . Almost all South Island genetic variation is found in the north of the island, consistent with refugia in Marlborough Sounds, central Nelson and northwest Nelson. All central and southern South Island and Stewart Island haplotypes are extremely similar to northern South Island haplotypes, a 'northern richness/southern purity' pattern that mirrors genetic patterns observed in many Northern Hemisphere taxa. Proposed southern South Island forest habitat fragments may have been too small to sustain populations of K. subalpina , and/or they may have harboured ecological communities with no modern-day analogues.     

Closing the gap: Avian lineage splits at a young,narrow seaway imply a protracted history of mixed population response

The evolutionary significance of spatial habitat gaps has been well recognized since Alfred Russel Wallace compared the faunas of Bali and Lombok. Gaps between islands influence population structuring of some species, and flightless birds are expected to show strong partitioning even where habitat gaps are narrow. We examined the population structure of the most numerous living flightless land bird in New Zealand, Weka (Gallirallus australis). We surveyed Weka and their feather lice in native and introduced populations using genetic data gathered from DNA sequences of mitochondrial genes and nuclear β‐fibrinogen and five microsatellite loci. We found low genetic diversity among extant Weka population samples. Two genetic clusters were evident in the mtDNA from Weka and their lice, but partitioning at nuclear loci was less abrupt. Many formerly recognized subspecies/species were not supported; instead, we infer one subspecies for each of the two main New Zealand islands. Although currently range restricted, North Island Weka have higher mtDNA diversity than the more wide‐ranging southern Weka. Mismatch and neutrality statistics indicate North Island Weka experienced rapid and recent population reduction, while South Island Weka display the signature of recent expansion. Similar haplotype data from a widespread flying relative of Weka and other New Zealand birds revealed instances of North Island—South Island partitioning associated with a narrow habitat gap (Cook Strait). However, contrasting patterns indicate priority effects and other ecological factors have a strong influence on spatial exchange at this scale.     

Phylogeography of a high‐dispersal New Zealand sea‐star: does upwelling block gene‐flow?

New Zealand's (NZ) geographical isolation, extensive coastline and well-characterized oceanography offer a valuable system for marine biogeographical research. Here we use mtDNA control region sequences in the abundant endemic sea-star Patiriella regularis to test the following literature-based predictions: that coastal upwelling disrupts north-south gene flow and promotes population differentiation (hypothesis 1); and that an invasive Tasmanian population of the species was introduced anthropogenically from southern New Zealand (hypothesis 2). We sequenced 114 samples from 22 geographical locations, including nine sites from North Island, nine from South Island, one from Stewart Island and three from Tasmania. Our analysis of these sequences revealed an abundance of shallow phylogenetic lineages within P. regularis (68 haplotypes, mean divergence 0.9%). We detected significant genetic heterogeneity between pooled samples from northern vs. southern New Zealand (FST = 0.072; P = 0.0002), consistent with the hypothesis that upwelling disrupts gene flow between these regions (hypothesis 1). However, we are currently unable to rule out the alternative hypothesis that Cook Strait represents a barrier to dispersal (North Island vs. South Island; FST = 0.031; P = 0.0467). The detection of significant spatial structure in NZ samples is consistent with restricted gene flow, and the strong structure evident in northern NZ may be facilitated by distinct ocean current systems. Four shared haplotypes and nonsignificant differentiation (FST = 0.025; P = 0.2525) between southern New Zealand and Tasmanian samples is consistent with an anthropogenic origin for the latter population (hypothesis 2).     

Nuclear mitochondrial pseudogenes as molecular outgroups for phylogenetically isolated taxa: a case study in Sphenodon

'Living fossil' taxa, by definition, have no close relatives, and therefore no outgroup to provide a root to phylogenetic trees. We identify and use a molecular outgroup in the sole extant lineage of sphenodontid reptiles, which separated from other reptiles 230 million years ago. We isolated and sequenced a partial nuclear copy of the mitochondrial cytochrome b gene. We confirm the copy is indeed not mitochondrial, is older than all extant mitochondrial copies in Sphenodon (tuatara), and is therefore useful as a molecular outgroup. Under phylogenetic analysis, the nuclear copy places the root of the tuatara mitochondrial gene tree between the northern and the southern (Cook Strait) groups of islands of New Zealand that are the last refugia for Sphenodon. This analysis supports a previous mid-point rooted mitochondrial gene tree. The mitochondrial DNA tree conflicts with allozyme analyses which place a Cook Strait population equidistant to all northern and other Cook Strait populations. This population on North Brother Island is the only natural population of extant S. guntheri; thus, we suggest that the current species designations of tuatara require further investigation.     

Extensive genetic differentiation in Gobiomorphus breviceps from New Zealand

Partial mitochondrial DNA sequences for parts of the cytochrome b gene and control region were obtained for 89 upland bullies Gobiomorphus breviceps from 19 catchments in New Zealand. There were two highly distinctive mtDNA clades: a northern clade corresponding to the North Island, northern South Island and west coast South Island, and a south‐east clade, in the southern and eastern South Island. Within these major clades there were further distinct clades that correlated with geographic sub‐regions and catchments. The marked genetic differentiation has occurred in the absence of obvious morphological divergence. Based on cytochrome b sequence divergences and the molecular clock hypothesis, the northern and southeastern clades correspond with the uplift of the Southern Alps during the Pliocene, while populations in the North Island and northern South Island were estimated to have diverged during the Pleistocene. The widescale geographic divergences were similar to those observed in the galaxiids, Galaxias vulgaris and Galaxias divergens , but biogeographic management boundaries may not be the same, reflecting different evolutionary histories for non‐diadromous species occupying the same areas.     

Historical biogeography of the New Zealand freshwater crayfishes (Parastacidae,Paranephrops spp.): Restoration of a refugial survivor?

Abstract

New Zealand's two species of freshwater parastacid crayfishes have allopatric distributions, with one species in the North Island and northwestern South Island and the other in the eastern and southern South Island and Stewart Island. This gives the appearance of a vicariance event driven by uplift of the Southern Alps beginning in the Pliocene, and of former land connections across both Cook Strait and Foveaux Strait. However, separation of the two species may date from before the Southern Alps were formed. A diverse series of historical geological events is invoked to explain details of the distributions of these two species. Absence of Paranephrops from intermontane valleys of eastern flanks of the Southern Alps is notably different from patterns seen in freshwater fish species.     

Low genetic divergence obscures phylogeny among populations of Sphenodon,remnant of an ancient reptile lineage

Tuatara (two species of Sphenodon) are the last representatives of a branch of an ancient reptilian lineage, Sphenodontia, that have been isolated on the New Zealand landmass for 82 million years. We present analyses of geographic variation in allozymes, mitochondrial DNA, nuclear DNA sequences, and one-way albumin immunological comparisons. These all confirm a surprisingly low level of genetic diversity within Sphenodon for such an ancient lineage. We hypothesise a recent extended population bottleneck, probably during the Pliocene/Pleistocene glaciation cycles, to explain the current paucity of variation. All data sets reveal clear genetic differentiation between the northern populations and those in Cook Strait, but offer conflicting views of the history and taxonomic relationships of the Cook Strait population on North Brother Island, currently recognised as Sphenodon guntheri. Allozymes show this population to be the most divergent of all tuatara populations, but preliminary mitochondrial DNA data indicate few differences between S. guntheri and Cook Strait Sphenodon punctatus. Interpretation of the trees is confounded by the lack of a suitable outgroup. As in other cases of conflicting nuclear and mitochondrial data sets, the different data sets likely reveal different aspects of the animals' evolutionary history, and introgression is not uncommon between species pairs.     

Phylogeography of two New Zealand lizards: McCann's skink (Oligosoma maccanni) and the brown skink (O. zelandicum)

The New Zealand skink fauna has proven to be an ideal taxonomic group in which to examine the impact of climatic and geological processes on the evolution of the New Zealand biota since the Pliocene. Here we examine the phylogeography of McCann's skink (Oligosoma maccanni) in order to gain insight into the relative contribution of Pliocene and Pleistocene processes on patterns of genetic structure in the South Island biota, and investigate the phylogeography of the brown skink (O. zelandicum) to examine whether Cook Strait landbridges facilitated geneflow between the North and South Islands in the late-Pleistocene. We obtained mitochondrial DNA sequence data (ND2 and ND4; 1282bp) from across the range of both species. We examined the phylogeographic patterns evident in each species using Neighbour-Joining, Maximum Likelihood and Bayesian methods. We found substantial phylogeographic structure within O. maccanni, with seven distinct clades identified. Divergences among clades are estimated to have occurred during the Pliocene. Populations in the Otago/Southland region (south of the Waitaki River valley) formed a well-supported lineage within O. maccanni. A substantial genetic break was evident between populations in east and west Otago, either side of the Nevis-Cardrona fault system, while north-south genetic breaks were evident within the Canterbury region. Within-clade divergences in O. maccanni appear to have occurred during the mid- to late-Pleistocene. Shimodaira-Hasegawa topology tests indicated that the 'Garston' skink is not genetically distinct from O. maccanni. There was only relatively minor phylogeographic structure within O. zelandicum, with divergences among populations occurring during the mid- to late-Pleistocene. Our genetic data supports a single colonisation of the North Island by O. zelandicum from the South Island, with the estimated timing of this event (0.46mya) consistent with the initial formation of Cook Strait.     

Variation in scope for growth: a test of food limitation among intertidal mussels

Wellington Harbour supports large populations of the mussels Aulacomya maoriana, Mytilus galloprovincialis and Perna canaliculus that are almost entirely absent from nearby coastal locations in Cook Strait. We calculated scope for growth (SFG) using ambient Cook Strait water over a broad temporal scale and a broad range of seston conditions to determine if negative SFG explains this phenomenon. Although all three mussel species had positive mean SFG values, variation in SFG was high and negative values often occurred: A. maoriana 19.1 J g⁻¹ h⁻¹, 43% of mussels showed negative SFG; M. galloprovincialis 1.26, 52% negative SFG; P. canaliculus 45.6, 27% negative SFG. Negative SFG was most often due to negative absorption efficiency caused by metabolic faecal loss that is characteristic of mussels feeding in environments with low seston quality. From our ecophysiology data we constructed a model to estimate SFG based on physiological responses to the narrow range of seston conditions typical of Cook Strait (Model One), and a model to estimate SFG based on physiological responses of mussels to the broad range of seston conditions typical of Wellington Harbour and Cook Strait (Model Two). We used seston data collected over an 18-month period from sites in Wellington Harbour and Cook Strait to derive 159 estimates of species-specific mussel SFG from both models. Both models produced higher estimates of SFG for mussels in the Harbour compared with those at Cook Strait sites. This was consistent with elevated particulate concentrations in the Harbour than at Cook Strait sites, and in agreement with previous studies. For Cook Strait mussels, both models produced negative estimates of net energy balance for long periods of time (several months), whereas for Harbour mussels negative SFG estimates were generally short in duration. We conclude that our short-term laboratory-based determinations of SFG and our long-term bioenergetics modelling estimates do not conclusively support the hypothesis of food limitation for three coexisting taxa of mussels in the intertidal region of Cook Strait, New Zealand. Handling editor: P. Viaroli     

Phylogeography of the snakeskin chiton Sypharochiton pelliserpentis (Mollusca: Polyplacophora) around New Zealand: are seasonal near‐shore upwelling events a dynamic barrier to gene flow?

We present a phylogeographic study of the New Zealand and Australian intertidal chiton Sypharochiton pelliserpentis that was conducted to ascertain levels of population connectivity and to investigate the effect of previously hypothesized general phylogeographic boundaries. The analysis incorporated both cytochrome oxidase subunit 1 sequence data (approximately 700 bp) and RFLP data from 29 populations around New Zealand, and from one Australian population, for a total of N = 472. The major population structure observed was a strong disjunction between northern and southern populations (Φ_ST = 0.47), with the genetic breaks located at Cloudy/Clifford Bay and Farewell Spit, at the northern tip of the South Island. This finding corresponds with a common phylogeographic barrier observed in a number of other marine invertebrates, highlighting its significance and ubiquity. A third barrier to gene flow was identified between Spirits Bay and Ahipara, around the northern tip of the North Island. All three of these areas that exhibit significant population disjunctions have strong near‐shore upwelling along with water current movement offshore, and these features are prevalent during the time of year when S. pelliserpentis spawns. That these seasonal hydrographic patterns contribute to the population structuring of S. pelliserpentis is supported by comparison with other phylogeographic studies of marine invertebrates, where the strength of this barrier seems to correlate with spawning season. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 552–563.     

Regional differences in the distribution of the sub-Saharan, West Eurasian, and South Asian mtDNA lineages in Yemen

Despite its key location for population movements out of and back into Africa, Yemen has not yet been sampled on a regional level for an investigation of sub-Saharan, West Eurasian, and South Asian genetic contributions. In this study, we present mitochondrial DNA (mtDNA) data for regionally distinct Yemeni populations that reveal different distributions of mtDNA lineages. An extensive database of mtDNA sequences from North and East African, Middle Eastern and Indian populations was analyzed to provide a context for the regional Yemeni mtDNA datasets. The groups of western Yemen appear to be most closely related to Middle Eastern and North African populations, while the eastern Yemeni population from Hadramawt is most closely related to East Africa. Furthermore, haplotype matches with Africa are almost exclusively confined to West Eurasian R0a haplogroup in southwestern Yemen, although more sub-Saharan L-type matches appear in more northern Yemeni populations. In fact, Yemeni populations have the highest frequency of R0a haplotypes detected to date, thus Yemen or southern Arabia may be the site of the initial expansion of this haplogroup. Whereas two variants of the sub-Saharan haplogroup M1 were detected only in southwestern Yemen close to the Bab el-Mandeb Strait, different non-African M haplotypes were detected at low frequencies (approximately 2%) in western parts of the country and at a higher frequency (7.5%) in the Hadramawt. We conclude that the Yemeni gene pool is highly stratified both regionally and temporally and that it has received West Eurasian, Northeast African, and South Asian gene flow.     

Reduced MHC variation in a threatened tuatara species

The relationship between neutral and adaptive genetic diversity is important to understand in assessing the implications of a population bottleneck. Fitness-related genes, such as those of the major histocompatibility complex (MHC), may be influenced by selection, and so retain diversity even when it is lost at neutral markers. We measured MHC class I variation in an archaic reptile species Sphenodon guntheri [North Brother Island (NBI) tuatara], which naturally occurs on one 4 ha island in Cook Strait, New Zealand, and has low levels of microsatellite diversity. MHC variation in S. guntheri was compared with microsatellite DNA variation, and with MHC variation in a large population of Sphenodon punctatus (Cook Strait tuatara) on Stephens Island. The NBI population shows significantly decreased levels of genetic diversity compared with the Stephens Island population. Only three different MHC sequences and three genotypes were found on NBI, compared with 15 sequences and 21 genotypes in a similar sample size from Stephens Island. Two sequences appear to be unique to the NBI population. The assortment of sequence variants into genotypes suggests strong gametic disequilibrium between two MHC class I loci in S. guntheri , and only two haplotypes that were present in Hardy–Weinberg proportions were identified. MHC diversity in NBI tuatara appears to be largely influenced by genetic drift, consistent with a recent population bottleneck. This may compromise the ability of this population to respond to novel disease threats.     

Contrasting patterns of mussel abundance at neighbouring sites: does recruitment limitation explain the absence of mussels on Cook Strait (New Zealand) shores?

Wellington Harbour (New Zealand) supports large populations of mussels (Aulacomya maoriana, Mytilus galloprovincialis and Perna canaliculus), whereas these species are absent from Cook Strait shores only a few km away. The density of planktonic mussel larvae and their recruitment rates to artificial substrates were investigated at harbour (with mussels) and Cook Strait (no mussels) sites to determine if a diminished or a zero larval supply and/or settlement explains the absence of mussels from Cook Strait shores. At both locations, larvae were collected from the plankton approximately monthly between September 1998 and February 2000, and recruitment rates to artificial substrates were estimated between March 2000 and February 2001. Planktonic larval densities were almost an order of magnitude greater within the harbour than at coastal sites (mean (±S.D.) density was 982 m⁻³ (±1478) with a peak density in September 1998 of 4207 m⁻³, compared with 106 (±94) and 381 m⁻³, respectively, in March 1999). Larval recruitment at harbour sites was also significantly greater than at coastal sites (mean (±S.D.) recruitment density was 2169 m⁻² (±4207) with a peak of ca. 211,425 m⁻² in July 2000, compared with 88 m⁻² (±86) and ca. 3700 m⁻², respectively, in February 2001). It has been suggested that “bottom up” regulation of community structure, principally via a diet of particulates low in organic matter, is the explanation for the absence of suspension feeding mussels from Cook Strait sites [Helson, J. G., 2001. An investigation into the absence of mussels (Perna canalicus, Aulacomya maoriana and Mytilus galloprovincialis) from the South Coast of Wellington, New Zealand. Unpublished PhD thesis, Victoria University of Wellington, 183 pp.], but given that planktonic larval supply and recruitment rates are much reduced at coastal sites, these data may also be important in explaining the absence. Whether current levels of recruitment are sufficient to maintain an adult population is at present unknown and requires further examination.     

The demographic history of the New Zealand short-tailed bat Mystacina tuberculata inferred from modified control region sequences

Short-tailed bats Mystacina tuberculata were widespread throughout the forest that dominated prehuman New Zealand, but extensive deforestation has restricted them to scattered populations in forest fragments. In a previous study, the species' intraspecific phylogeny was investigated using multiple mitochondrial gene sequences. Six phylogroups were identified with estimated divergences of 0.93-0.68 Ma. In the current study, the phylogeographical structure and demographic history of the phylogroups were investigated using control region sequences modified by removing homoplasic sites. Phylogeographical structure in the North Island was generally consistent with an isolation-by-distance dispersal model. Coalescent-based analyses (i.e. mismatch distributions, skyline plots, lineage dispersal analysis and nested clade analysis) indicated that the three phylogroups found in central and southern North Island expanded before the last glacial maximum, presumably during interstadials when Nothofagus forest was most extensive. Genetic structure within a central North Island hybrid zone was consistent with range expansion from separate refugia following reforestation after catastrophic volcanic eruptions. Phylogeographical structure in the South Island was consistent with southern populations originating during rapid southward range expansion from refugia in northern South Island following postglacial reforestation of the South Island 10-9 kya.     

Detection of Ancestry Informative HLA Alleles Confirms the Admixed Origins of Japanese Population

The polymorphisms in the human leukocyte antigen (HLA) region are powerful tool for studying human evolutionary processes. We investigated genetic structure of Japanese by using five-locus HLA genotypes (HLA-A, -B, -C, -DRB1, and -DPB1) of 2,005 individuals from 10 regions of Japan. We found a significant level of population substructure in Japanese; particularly the differentiation between Okinawa Island and mainland Japanese. By using a plot of the principal component scores, we identified ancestry informative alleles associated with the underlying population substructure. We examined extent of linkage disequilibrium (LD) between pairs of HLA alleles on the haplotypes that were differentiated among regions. The LDs were strong and weak for pairs of HLA alleles characterized by low and high frequencies in Okinawa Island, respectively. The five-locus haplotypes whose alleles exhibit strong LD were unique to Japanese and South Korean, suggesting that these haplotypes had been recently derived from the Korean Peninsula. The alleles characterized by high frequency in Japanese compared to South Korean formed segmented three-locus haplotype that was commonly found in Aleuts, Eskimos, and North- and Meso-Americans but not observed in Korean and Chinese. The serologically equivalent haplotype was found in Orchid Island in Taiwan, Mongol, Siberia, and Arctic regions. It suggests that early Japanese who existed prior to the migration wave from the Korean Peninsula shared ancestry with northern Asian who moved to the New World via the Bering Strait land bridge. These results may support the admixture model for peopling of Japanese Archipelago.     

Ancient DNA Reveals That the Genetic Structure of the Northern Han Chinese Was Shaped Prior to 3,000 Years Ago

The Han Chinese are the largest ethnic group in the world, and their origins, development, and expansion are complex. Many genetic studies have shown that Han Chinese can be divided into two distinct groups: northern Han Chinese and southern Han Chinese. The genetic history of the southern Han Chinese has been well studied. However, the genetic history of the northern Han Chinese is still obscure. In order to gain insight into the genetic history of the northern Han Chinese, 89 human remains were sampled from the Hengbei site which is located in the Central Plain and dates back to a key transitional period during the rise of the Han Chinese (approximately 3,000 years ago). We used 64 authentic mtDNA data obtained in this study, 27 Y chromosome SNP data profiles from previously studied Hengbei samples, and genetic datasets of the current Chinese populations and two ancient northern Chinese populations to analyze the relationship between the ancient people of Hengbei and present-day northern Han Chinese. We used a wide range of population genetic analyses, including principal component analyses, shared mtDNA haplotype analyses, and geographic mapping of maternal genetic distances. The results show that the ancient people of Hengbei bore a strong genetic resemblance to present-day northern Han Chinese and were genetically distinct from other present-day Chinese populations and two ancient populations. These findings suggest that the genetic structure of northern Han Chinese was already shaped 3,000 years ago in the Central Plain area.     

Post-ice age recolonization and differentiation of Fucus serratus L. (Phaeophyceae; Fucaceae) populations in Northern Europe

The seaweed Fucus serratus is hypothesized to have evolved in the North Atlantic and present populations are thought to reflect recolonization from a southern refugium since the last glacial maximum 18 000-20 000 years bp. We examined genetic structure across several spatial scales by analysing seven microsatellite loci in populations collected from 21 localities throughout the species' range. Spatial auto-correlation analysis of seven microsatellite loci revealed no evidence for spatial clustering of alleles on a scale of 100 m despite limited gamete dispersal in F. serratus of approximately 2 m from parental individuals. Pairwise theta analysis suggested that the minimal panmictic unit for F. serratus was between 0.5 and 2 km. Isolation by distance was significant along some contiguous coastlines. Population differentiation was strong within the Skagerrak-Kattegat-Baltic Seas (SKB) (global theta= 0.17) despite a short history of approximately 7500 years. A neighbour-joining tree based on Reynold's distances computed from the microsatellite data revealed a central assemblage of populations on the Brittany Peninsula surrounded by four well-supported clusters consisting of the SKB, the North Sea (Ireland, Helgoland), and two populations from the northern Spanish coast. Samples from Iceland and Nova Scotia were most closely aligned with northwest Sweden and Brittany, respectively. When sample sizes were standardized (N = 41), allelic diversity was twofold higher for Brittany populations than for populations to the north and threefold higher than southern populations. The Brittany region may be a refugium or a recolonized area, whereas the Spanish populations most likely reflect present-day edge populations that have undergone repeated bottlenecks as a consequence of thermally induced cycles of recolonization and extinction.     

Mitochondrial phylogeography of New Zealand freshwater crayfishes, Paranephrops spp

Tectonic movement at the boundary of the Indo-Australian and Pacific Plates during the Miocene and Pliocene is recognized as a driving force for invertebrate speciation in New Zealand. Two endemic freshwater crayfish (koura) species, Paranephrops planifrons White 1842 and Paranephrops zealandicus White 1842, represent good model taxa to test geological hypotheses because, due to their low dispersal capacity and life history, geographical restriction of populations may be caused by vicariant processes. Analysis of a mitochondrial DNA marker (cytochrome oxidase subunit I) reveals not two, but three major koura lineages. Contrary to expectation, the cryptic West Coast group appears to be more closely related to P. zealandicus than to P. planifrons and has diverged earlier than the final development (Late Pleistocene) of Cook Strait. Our date estimates suggest that koura lineage diversification probably coincided with early to mid-Alpine orogeny in the mid-Pliocene. Estimates of node ages and the phylogenies are inconsistent with both ancient Oligocene and recent postglacial Pleistocene range expansion, but suggest central to north colonization of North Island and west to east movement in South Island during mid- to late Pliocene. Crypsis and paraphyly of the West Coast group suggest that morphological characters presently used to classify koura species could be misleading.     

Mitochondrial evidence for distinct phylogeographic units in the endangered Malagasy poison frog Mantella bernhardi

Mantella bernhardi is an endemic species of Malagasy poison frog threatened by loss and fragmentation of its natural habitat and collection for the pet trade. It is classified as threatened according to the International Union for Conservation of Nature and Natural Resources (IUCN) categories and included in Appendix II of the Convention on the International Trade of Endangered Species (CITES). A recent survey has increased the known distributional range of the species from one to eight populations across southeastern Madagascar, but little is known about its biology and genetic diversity. Here we estimate inter- and intrapopulation mitochondrial genetic variation of four populations. Populations from the northern and southern parts of the distributional range showed a high degree of divergence (maximum of 11.35% in cytochrome b) and were recovered as reciprocally monophyletic groups. Nine haplotypes were detected in the northern and 12 in the southern populations. The population from Ranomafana National Park showed the lowest number of haplotypes and nucleotide diversity, and shared its most common haplotype with the second northern population from Tolongoina. All the other detected haplotypes were unique to each of the four populations. This suggests the existence of important barriers to gene flow, pre-dating human colonization of Madagascar at about 2000 years ago, in distinct contrast to other Mantella species that show a high degree of haplotype sharing throughout their range. The continued habitat fragmentation within the distribution range of M. bernhardi prevents any connection between its populations. Our data indicate the existence of at least two different management units for conservation in this species, corresponding to the North and South of its distribution range, and highlight the existence of strong regional endemism in southeastern Madagascar.