Phylogeography of southern New Zealand: Implications of Pliocene and Pleistocene Processes and Evolutionary Concordance Across Independent Loci

<p>The endemic fauna of the South Island has proven to be an ideal taxonomic group to examine the impact of climatic and geological processes on the evolution of New Zealand's biota since the Pliocene. This thesis examines the phylogeography of McCann's skink (Oligosoma maccanni) in order to provide insight into the relative contribution of Pliocene and Pleistocene processes on patterns of genetic structure in South Island biota. This thesis also investigates the phylogeography of the brown skink (O. zelandicum) to examine whether Cook Strait landbridges facilitated gene flow between the North and South Island in the late-Pleistocene. This thesis also investigates the presence of genealogical concordance across independent loci for the endemic alpine stick insect, Niveaphasma. I obtained mitochondrial DNA (mtDNA) sequence data (ND2 and ND4; 1284 bp) from across the range of both skink species and mtDNA (COI; 762 bp) and nuclear sequence data (EF1 ; 590 bp) from across the range of Niveaphasma. I used DGGE in order to resolve nuclear EF1 alleles and examined phylogeographic patterns in each species using Neighbour-Joining, Maximum Likelihood and Bayesian methods. Substantial phylogeographic structure was found within O. maccanni, with divergences among clades estimated to have occurred during the Pliocene. Populations in the Otago/Southland region formed a well-supported lineage within O. maccanni. A genetic break was evident between populations in east and west Otago, while north-south genetic breaks were evident within the Canterbury region. There was relatively minor phylogeographic structure within O. zelandicum. Our genetic data supports a single colonization of the North Island by O. zelandicum from the South Island, with the estimated timing of this event (0.46 Mya) consistent with the initial formation of Cook Strait. There was substantial genetic structuring identified within Niveaphasma, with a well-supported lineage present in the Otago/Southland region. There was also a genetic break between populations in Canterbury and eastern Otago with those in central Otago and Southland. The genetic data provided strong genealogical concordance between mtDNA haplotypes and nuclear alleles suggesting an accurate depiction of the historical isolation identified between the major clades of Niveaphasma. This finding offers compelling evidence for the use of nuclear gene phylogeography alongside mtDNA for future evolutionary studies within New Zealand.</p>

Phylogeography of southern New Zealand: Implications of Pliocene and Pleistocene Processes and Evolutionary Concordance Across Independent Loci

<p>The endemic fauna of the South Island has proven to be an ideal taxonomic group to examine the impact of climatic and geological processes on the evolution of New Zealand's biota since the Pliocene. This thesis examines the phylogeography of McCann's skink (Oligosoma maccanni) in order to provide insight into the relative contribution of Pliocene and Pleistocene processes on patterns of genetic structure in South Island biota. This thesis also investigates the phylogeography of the brown skink (O. zelandicum) to examine whether Cook Strait landbridges facilitated gene flow between the North and South Island in the late-Pleistocene. This thesis also investigates the presence of genealogical concordance across independent loci for the endemic alpine stick insect, Niveaphasma. I obtained mitochondrial DNA (mtDNA) sequence data (ND2 and ND4; 1284 bp) from across the range of both skink species and mtDNA (COI; 762 bp) and nuclear sequence data (EF1 ; 590 bp) from across the range of Niveaphasma. I used DGGE in order to resolve nuclear EF1 alleles and examined phylogeographic patterns in each species using Neighbour-Joining, Maximum Likelihood and Bayesian methods. Substantial phylogeographic structure was found within O. maccanni, with divergences among clades estimated to have occurred during the Pliocene. Populations in the Otago/Southland region formed a well-supported lineage within O. maccanni. A genetic break was evident between populations in east and west Otago, while north-south genetic breaks were evident within the Canterbury region. There was relatively minor phylogeographic structure within O. zelandicum. Our genetic data supports a single colonization of the North Island by O. zelandicum from the South Island, with the estimated timing of this event (0.46 Mya) consistent with the initial formation of Cook Strait. There was substantial genetic structuring identified within Niveaphasma, with a well-supported lineage present in the Otago/Southland region. There was also a genetic break between populations in Canterbury and eastern Otago with those in central Otago and Southland. The genetic data provided strong genealogical concordance between mtDNA haplotypes and nuclear alleles suggesting an accurate depiction of the historical isolation identified between the major clades of Niveaphasma. This finding offers compelling evidence for the use of nuclear gene phylogeography alongside mtDNA for future evolutionary studies within New Zealand.</p>

Barrier to Gene Flow of Grey Mangrove Avicennia marina Populations in the Malay Peninsula as Revealed From Nuclear Microsatellites and Chloroplast Haplotypes

Contemporary mangrove forest areas took shape historically and their genetic connectivity depends on sea-faring propagules, subsequent settlement, and persistence in suitable environments. Mangrove species world-wide may experience genetic breaks caused by major land barriers or opposing ocean currents influencing their population genetic structure. For Malay Peninsula, several aquatic species showed strong genetic differentiation between East and West coast regions due to the Sunda shelf flooding since the Last Glacial Maximum. In this study genetic diversity and structure of Avicennia marina populations in Malay Peninsula were assessed using nuclear microsatellite markers and chloroplast sequences. Even though all populations showed identical morphological features of A. marina, three evolutionary significant units were obtained with nuclear and cytoplasmic markers. Avicennia marina along a 586 km stretch of the West coast differed strongly from populations along an 80 km stretch of the East coast featuring chloroplast capture of Avicennia alba in an introgressive A. marina. Over and above this expected East-West division, an intra-regional subdivision was detected among A. marina populations in the narrowest region of the Strait of Malacca. The latter genetic break was supported by an amova, structure, and barrier analysis whereas RST &gt; FST indicated an evolutionary signal of long-lasting divergence. Two different haplotypes along the Western coast showed phylogeographic relationship with either a northern or a putative southern lineage, thereby assuming two Avicennia sources facing each other during Holocene occupation with prolonged separation in the Strait of Malacca. Migrate-n model testing supported a northward unidirectional stepping-stone migration route, although with an unclear directionality at the genetic break position, most likely due to weak oceanic currents. Low levels of genetic diversity and southward connectivity was detected for East coast Avicennia populations. We compared the fine-scale spatial genetic structure (FSGS) of Avicennia populations along the exposed coast in the East vs. the sheltered coast in the West. A majority of transects from both coastlines revealed no within-site kinship-based FSGS, although the remoteness of the open sea is important for Avicennia patches to maintain a neighborhood. The results provide new insights for mangrove researchers and managers for future in-depth ecological-genetic-based species conservation efforts in Malay Peninsula.

Genetic Structure of the Goniopora lobata and G. djiboutiensis Species Complex Is Better Explained by Oceanography Than by Morphological Characteristics

Species delimitation of closely related corals is often challenging due to high intraspecies morphological variation and phenotypic plasticity with a lack of characteristic features and scarcity of relevant molecular markers. Goniopora spp. are one such coralline group, and the species status of Goniopora lobata and Goniopora djiboutiensis, an Indian and Pacific Ocean hermatypic coral species complex, has been questioned on the basis of previous molecular and morphological analyses. To further examine the species boundaries between G. lobata and G. djiboutiensis in Japan, specimens collected from areas spanning from Ryukyu Island to temperate Japanese regions were morphologically identified based on traditional morphological descriptions. Then, the genetic structure of the G. lobata and G. djiboutiensis species complex was examined using six newly developed microsatellite markers. The majority of the collected specimens had intermediate morphologies, and a STRUCTURE analysis using the LOCPRIOR model based on typical G. lobata and G. djiboutiensis morphology indicated that there were no genetic differences between these morphologies. On the other hand, STRUCTURE analysis based on oceanographic regions revealed that there was a genetic break between the temperate and subtropical regions. This weak genetic break corresponded with the Kuroshio-associated barrier, which prevents larval transport between subtropical and temperate regions. This study confirms that the current morphological identification criteria for G. lobata and G. djiboutiensis do not match the existing genetic boundaries and thus the two should be regarded as a species complex. This study also highlighted the robustness of using a multi-locus population genetic approach, including a geographic context, to confirm the species boundaries of closely related species.

Spatial genetic patterns of Octopus vulgaris Mediterranean populations support the hypothesis of a transitional zone across the Siculo-Tunisian Strait

Recent research hypothesised that the Siculo-Tunisian Strait might fit, at least for some species, the picture of a genetic transitional zone instead of a sharp genetic break between the Western and Eastern Mediterranean basins. The present study aimed at using the common Octopus, Octopus vulgaris as an empirical test-case to evaluate this hypothesis. To accomplish this goal, 458 new sequences of the mitochondrial gene cytochrome c oxidase subunit I were used. Combining the new sequences with those available on public databases, we assembled a dataset containing 920 sequences to investigate the spatial genetic patterns across 34 Mediterranean populations of O. vulgaris. The genetic structure of this species was assessed combining analysis of molecular variance and Median-Joining networks. Results supported the hypothesis of a complex spatial genetic pattern across the Sicilian channel. Contemporary factors, such as marine currents, likely affect the species’ genetic structuring across this area. Overall, our results highlighted that focusing the attention on the whole transitional area rather than on a unique genetic break might help to detect similar patterns across different species. Finally, acknowledging the occurrence of complex spatial genetic patterns across transitional zones may improve stock identification and management practices for commercially valuable species.

Contrasting Phylogeographic Patterns in Lumnitzera Mangroves Across the Indo-West Pacific

Mangroves are ecologically important forest communities in tropical and subtropical coasts, the effective management of which requires understanding of their phylogeographic patterns. However, these patterns often vary among different species, even among ecologically similar taxa or congeneric species. Here, we investigated the levels and patterns of genetic variation within Lumnitzera consisting of two species (L. racemosa and L. littorea) with nearly sympatric ranges across the Indo-West Pacific (IWP) region by sequencing three chloroplast DNA regions (for both species) and genotyping 11 nuclear microsatellite loci (for L. littorea). Consistent with findings in studies on other mangrove species, we found that both L. racemosa and L. littorea showed relatively high genetic variation among populations but low genetic variation within populations. Haplotype network and genetic clustering analyses indicated two well-differentiated clades in both L. racemosa and L. littorea. The relationship between geographic and genetic distances and divergence time estimates of the haplotypes indicated that limited dispersal ability of the propagules, emergence of land barriers during ancient sea-level changes, and contemporary oceanic circulation pattern in the IWP influenced the current population structure of the two species. However, the position of genetic break was found to vary between the two species: in L. racemosa, strong divergence was observed between populations from the Indian Ocean and the Pacific Ocean possibly due to land barrier effect of the Malay Peninsula; in L. littorea, the phylogeographic pattern was created by a more eastward genetic break along the biogeographic barrier identified as the Huxley’s line. Overall, our findings strongly supported previous hypothesis of mangrove species divergence and revealed that the two Lumnitzera species have different phylogeographic patterns despite their close genetic relationship and similar current geographic distribution. The findings also provided references for the management of Lumnitzera mangroves, especially for the threatened L. littorea.

Population structure and dispersal across small and large spatial scales in a direct developing marine isopod

Marine organisms generally exhibit one of two developmental modes: biphasic, with distinct adult and larval morphology, and direct development, in which larvae resemble adults. Developmental mode is thought to significantly influence dispersal, with direct developers expected to have much lower dispersal potential. However, in contrast to our relatively good understanding of dispersal and population connectivity for biphasic species, comparatively little is known about direct developers. In this study, we use a panel of 8,020 SNPs to investigate population structure and gene flow for a direct developing species, the New Zealand endemic marine isopod Isocladus armatus. On a small spatial scale (20 kms), gene flow between locations is extremely high and suggests an island model of migration. However, over larger spatial scales (600km), populations exhibit a clear pattern of isolation-by-distance. Because our sampling range is intersected by two well-known biogeographic barriers (the East Cape and the Cook Strait), our study provides an opportunity to understand how such barriers influence dispersal in direct developers. Our results indicate that I. armatus exhibits significant migration across these barriers, and suggests that ocean currents associated with these locations do not present a barrier to dispersal. Interestingly, we do find evidence of a north-south population genetic break occurring between Māhia and Wellington, two locations where there are no obvious biogeographic barriers between them. We conclude that developmental life history largely predicts dispersal in intertidal marine isopods. However, localised biogeographic processes can disrupt this expectation.

The genetic divergence of Oratosquilla oratoria between the East China Sea and Yellow Sea: physical barrier and possible local adaptation

In order to confirm the genetic relationship between the Yellow Sea and East China Sea populations of mantis shrimps Oratosquilla oratoria, fragments of mitochondrial DNA COI gene samples were analysed. A total of 212 individuals from nine localities in the East China Sea and Yellow Sea were collected and 108 haplotypes were detected. Neighbour-joining analysis revealed a complete genetic break between the Yellow Sea and East China Sea, which was consistent with the previous mtDNA 16S rRNA. Pleistocene isolation and the current physical barrier were responsible for the complete genetic break between the East China Sea and Yellow Sea. Furthermore, local adaptation in the COI gene may also be contributed to by the genetic differentiation between the populations of the Yellow Sea and East China. The different Ka/Ks ratios between the two clades may reflect different selection pressures and local adaptation on the fragment of COI gene.