The evolution of black plumage from blue in Australian fairy‐wrens (Maluridae): genetic and structural evidence

Genetic variation in the melanocortin‐1 receptor (MC1R) locus is responsible for color variation, particularly melanism, in many groups of vertebrates. Fairy‐wrens, Maluridae, are a family of Australian and New Guinean passerines with several instances of dramatic shifts in plumage coloration, both intra‐ and inter‐specifically. A number of these color changes are from bright blue to black plumage. In this study, we examined sequence variation at the MC1R locus in most genera and species of fairy‐wrens. Our primary focus was subspecies of the white‐winged fairy‐wren Malurus leucopterus in which two subspecies, each endemic to islands off the western Australian coast, are black while the mainland subspecies is blue. We found fourteen variable amino acid residues within M. leucopterus, but at only one position were alleles perfectly correlated with plumage color. Comparison with other fairy‐wren species showed that the blue mainland subspecies, not the black island subspecies, had a unique genotype. Examination of MC1R protein sequence variation across our sample of fairy‐wrens revealed no correlation between plumage color and sequence in this group. We thus conclude that amino acid changes in the MC1R locus are not directly responsible for the black plumage of the island subspecies of M. leucopterus. Our examination of the nanostructure of feathers from both black and blue subspecies of M. leucopterus and other black and blue fairy‐wren species clarifies the evolution of black plumage in this family. Our data indicate that the black white‐winged fairy‐wrens evolved from blue ancestors because vestiges of the nanostructure required for the production of blue coloration exist within their black feathers. Based on our phylogeographic analysis of M. leucopterus, in which the two black subspecies do not appear to be each other's closest relatives, we infer that there have been two independent evolutionary transitions from blue to black plumage. A third potential transition from blue to black appears to have occurred in a sister clade.     

Declining populations in one of the last refuges for threatened mammal species in northern Australia

Australia has contributed a disproportionate number of the world's mammal extinctions over the past 200 years, with the greatest loss of species occurring through the continent's southern and central arid regions. Many taxonomically and ecologically similar species are now undergoing widespread decline across the northern Australian mainland, possibly driven by predation by feral cats and changed fire regimes. Here, we report marked recent declines of native mammal species in one of Australia's few remaining areas that support an intact mammal assemblage, Melville Island, the largest island off the northern Australian coast. We have previously reported a marked decline on Melville Island of the threatened brush‐tailed rabbit‐rat (Conilurus penicillatus) over the period 2000–2015, linked to predation by feral cats. We now report a 62% reduction in small mammal trap‐success and a 36% reduction in site‐level species richness over this period. There was a decrease in trap‐success of 90% for the northern brown bandicoot (Isoodon macrourus), 64% for the brush‐tailed rabbit‐rat and 63% for the black‐footed tree‐rat (Mesembriomys gouldii), but no decline for the common brushtail possum (Trichosurus vulpecula). These results suggest that populations of native mammals on Melville Island are exhibiting similar patterns of decline to those recorded in Kakadu National Park two decades earlier, and across the northern Australian mainland more generally. Without the implementation of effective management actions, these species are likely to be lost from one of their last remaining strongholds, threatening to increase Australia's already disproportionate contribution to global mammal extinctions.     

Interspecific variation in avian blood parasites and haematology associated with urbanization in a desert habitat

Many avian species are negatively impacted by urbanization, but other species survive and prosper in urbanized areas. One factor potentially contributing to the success of some species in urban areas is the reduced presence of predators or parasite vectors in urban compared to rural areas. In addition, urban areas may provide increased food and water resources, which can enhance immune capacity to resist infection and the ability to eliminate parasites. We determined patterns of blood parasitism, body condition, and immune cell profiles in urban and rural populations of five adult male songbird species that vary in their relative abundance within urban areas. Urban birds generally exhibited less blood parasitism than rural birds. This difference was particularly evident for the urban-adaptable Abert's towhee Pipilo aberti . In contrast, no difference in haemoparasitism was seen between urban and rural populations of the curve-billed thrasher Toxostoma curvirostre , a less-urban adaptable species. In two closely related species, the curve-billed thrasher and the northern mockingbird Mimus polyglottos , urban birds had a higher leukocyte count and a higher heterophil to lymphocyte ratio, which is often associated with chronic stress or current infection, than rural birds. Urban northern mockingbirds were in better condition than rural counterparts, but no habitat-related differences in condition were detected for other species. Parasitic infection was correlated with body condition in only one species, the canyon towhee Pipilo fuscus . Parasitic infection in most species was correlated with changes in leukocyte abundance and profile. The findings suggest that interspecific differences in parasitic infection cannot be attributed entirely to differences in vector abundance or body condition. Interactions between immune function, parasite infection risk, and resource availability may contribute to determining the relative ability of certain species to adapt to cities.     

Molecular markers provide insights into contemporary and historic gene flow for a non‐migratory species

Hairy woodpeckers Picoides villosus are a common, year round resident with distinct plumage and morphological variation across North America. We genotyped 335 individuals at six variable microsatellite loci and analyzed 322 mtDNA control region sequences in order to examine the role of contemporary and historical barriers to gene flow. In addition we combined genetic analyses with ecological niche modelling to test if hairy woodpeckers were isolated in northern refugia (Alaska, Newfoundland and the Queen Charlotte Islands) during the last glacial maximum. Genetic analyses revealed that gene flow among North American hairy woodpecker populations is restricted, but not to the extent predicted for a sedentary species. Populations clustered into two main genetic groups, east and west of the Great Plains in the south and the Rocky Mountains in the north. Contact zones between the two main genetic groups exist in central British Columbia and Washington, but are narrow. Within each group we found additional population structure with genetic breaks between subgroups in the geographic west corresponding to breaks in forested habitat and physical barriers like open expanses of water. Population genetic patterns for hairy woodpeckers have resulted from isolation in multiple southern refugia with the current distribution of genetic groups resulting from post‐glacial expansion and subsequent reduction in gene flow. While populations in Alaska, Newfoundland and the Queen Charlotte Islands are genetically distinct from other populations, we found no evidence of these areas acting as refugia throughout the Pleistocene. Atlantic Canada populations contained unique haplotypes raising the possibility of a separate colonization from the rest of eastern Canada. The endemic subspecies on the island of Newfoundland is not genetically distinct from their closest mainland population unlike the Queen Charlotte Island subspecies.     

Genetic differentiation of the Thorn‐tailed Rayadito Aphrastura spinicauda (Furnariidae: Passeriformes) revealed by ISSR profiles suggests multiple palaeorefugia and high recurrent gene flow

Nucleotide sequence data (cytochrome b) and ISSR genomic fingerprints were used to analyse the genetic variation and population differentiation in Thorn‐tailed Rayadito, a widespread Patagonian forest bird. We included samples from eight populations of Thorn‐tailed Rayadito covering most of the distribution range of the species: from fragmented patches of Olivillo forest in northern Chile to Isla Navarino forests in the extreme south of South America. Low levels of genetic diversity were found among populations, with a large within‐population molecular variance indicating high levels of gene flow. The multivariate and cluster analyses based on ISSR markers show that the subspecies bullocki (from Mocha Island) differs significantly from all other populations. The subspecies fulva (Chiloé Island) shows less differentiation than bullocki, sharing several alleles with continental populations. Bayesian analyses suggest that the Mocha Island population contributes most to the total genetic diversity observed in the species. Mantel tests revealed no significant correlation between geographical distance and pairwise genetic distance and cytochrome b sequence analyses failed to detect differentiation among subspecies. Mocha Island might have been a palaeorefuge and this population may have diversified by genetic drift after the last glacial maximum. There is also the possibility of a postglacial colonization of the Thorn‐tailed Rayadito from an austral palaeorefugium, supporting a multiple refugia hypothesis. This study illustrates the usefulness of the rarely used ISSR genomic fingerprint method in avian phylogeography.     

Population structure of caribou in an ice‐bound archipelago

Aim

Archipelagos provide ideal natural systems for testing the effects of isolation and fragmentation of habitats on the genetic makeup of populations—an important consideration, given that many insular species are of conservation concern. Two theories predominate: Island Biogeography Theory (IBT) posits that proximity to the mainland drives the potential for migrants and gene flow. The Central Marginal Hypothesis (CMH) predicts that island populations at the periphery of a species range may experience low gene flow, small population size and high rates of genetic drift. We investigated population genetic structure, genetic diversity and key drivers of diversity for Arctic island‐dwelling caribou (Rangifer tarandus). Our aim was to inform intraspecific units for conservation and decipher how IBT and CMH could act in an archipelago where isolation is highly variable due to sea ice and open water.

Location

Canadian Arctic Archipelago, Canada (Latitude, 55–82°N; Longitude, 61–123°W).

Methods

We genotyped 447 caribou at 16 microsatellite loci; these caribou represented two subspecies (R. t. groenlandicus, R. t. pearyi) and three designatable units. We used hierarchical Bayesian clustering and ordination to determine genetic groups. We evaluated the influence of ecological and geographic variables on genetic diversity using linear mixed‐effects models and compared diversity among mainland and island herds.

Results

Bayesian clustering revealed nine genetic clusters with differentiation among and within caribou subspecies. Genetic differentiation was explained predominantly by isolation‐by‐distance across all caribou, even at the scale of subspecies. Island caribou were less genetically diverse than mainland herds; individual heterozygosity was negatively correlated with distance‐to‐mainland and the extent of autumn ice‐free coastline and positively correlated with unglaciated island size.

Main conclusions

Our findings underscore the importance of hierarchical analysis when investigating genetic population structure. Genetic diversity and its key drivers lend support to both IBT and CMH and highlight the pending threat of climate change for Arctic island caribou.

     

Integrated species delimitation and conservation implications of an endangered weevil Pachyrhynchus sonani (Coleoptera: Curculionidae) in Green and Orchid Islands of Taiwan

Oceanic islands are productive habitats for generating new species and high endemism, which is primarily due to their geographical isolation, smaller population sizes and local adaptation. However, the short divergence times and subtle morphological or ecological divergence of insular organisms may obscure species identity, so the cryptic endemism on islands may be underestimated. The endangered weevil Pachyrhynchus sonani Kôno (Coleoptera: Curculionidae: Entiminae: Pachyrhynchini) is endemic to Green Island and Orchid Island of the Taiwan‐Luzon Archipelago and displays widespread variation in coloration and host range, thus raising questions regarding its species boundaries and degree of cryptic diversity. We tested the species boundaries of P. sonani using an integrated approach that combined morphological (body size and shape, genital shape, coloration and cuticular scale), genetic (four genes and restriction site‐associated DNA sequencing, RAD‐seq) and ecological (host range and distribution) diversity. The results indicated that all the morphological datasets for male P. sonani, except for the colour spectrum, reveal overlapping but statistically significant differences between islands. In contrast, the morphology of the female P. sonani showed minimum divergence between island populations. The populations of P. sonani on the two islands were significantly different in their host ranges, and the genetic clustering and phylogenies of P. sonani established two valid evolutionary species. Integrated species delimitation combining morphological, molecular and ecological characters supported two distinct species of P. sonani from Green Island and Orchid Island. The Green Island population was described as P. jitanasaius sp.n. Chen & Lin, and it is recommended that its threatened conservation status be recognized. Our findings suggest that the inter‐island speciation of endemic organisms inhabiting both islands may be more common than previously thought, and they highlight the possibility that the cryptic diversity of small oceanic islands may still be largely underestimated.     

Does relaxed predation drive phenotypic divergence among insular populations?

The evolution of striking phenotypes on islands is a well‐known phenomenon, and there has been a long‐standing debate on the patterns of body size evolution on islands. The ecological causes driving divergence in insular populations are, however, poorly understood. Reduced predator fauna is expected to lower escape propensity, increase body size and relax selection for crypsis in small‐bodied, insular prey species. Here, we investigated whether escape behaviour, body size and dorsal coloration have diverged as predicted under predation release in spatially replicated islet and mainland populations of the lizard species Podarcis gaigeae. We show that islet lizards escape approaching observers at shorter distances and are larger than mainland lizards. Additionally, we found evidence for larger between‐population variation in body size among the islet populations than mainland populations. Moreover, islet populations are significantly more divergent in dorsal coloration and match their respective habitats poorer than mainland lizards. These results strongly suggest that predation release on islets has driven population divergence in phenotypic and behavioural traits and that selective release has affected both trait means and variances. Relaxed predation pressure is therefore likely to be one of the major ecological factors driving body size divergence on these islands.     

Notes on the geographic distribution of howling monkeys in the marajó archipelago, pará, Brazil

I review the distribution of genus Alouattain the Marajó Archipelago based on geographic variation of pelage color patterns. Specific differences exist among the labeled specimens at Museu Paraense Emílio Goeldi, which are confirmed via new field information from wild populations. The animals from Marajó, Caviana, and Mexiana Islands possess color patterns of Alouatta belzebul,while Alouatta seniculusis confirmed as the species that inhabits Gurupá Island. The high variability of pelage coloration of the animals from Marajó, Caviana, and Mexiana Islands includes all phenotypes formerly designated as different subspecies. The howler populations from these three islands belong to the same subspecies as those populations that inhabit the region of Tucurui dam reservoir (area 4). Finally, it seems that, as also suggested by chromosome studies, A. belzebulprobably comprises different epiphenotypes without taxonomic validity.     

Genetic and phylogenetic consequences of island biogeography

Abstract.— Island biogeography theory predicts that the number of species on an island should increase with island size and decrease with island distance to the mainland. These predictions are generally well supported in comparative and experimental studies. These ecological, equilibrium predictions arise as a result of colonization and extinction processes. Because colonization and extinction are also important processes in evolution, we develop methods to test evolutionary predictions of island biogeography. We derive a population genetic model of island biogeography that incorporates island colonization, migration of individuals from the mainland, and extinction of island populations. The model provides a means of estimating the rates of migration and extinction from population genetic data. This model predicts that within an island population the distribution of genetic divergences with respect to the mainland source population should be bimodal, with much of the divergence dating to the colonization event. Across islands, this model predicts that populations on large islands should be on average more genetically divergent from mainland source populations than those on small islands. Likewise, populations on distant islands should be more divergent than those on close islands. Published observations of a larger proportion of endemic species on large and distant islands support these predictions.     

Notes on the geographic distribution of howling monkeys in the marajó archipelago,pará, Brazil

I review the distribution of genus Alouattain the Marajó Archipelago based on geographic variation of pelage color patterns. Specific differences exist among the labeled specimens at Museu Paraense Emílio Goeldi, which are confirmed via new field information from wild populations. The animals from Marajó, Caviana, and Mexiana Islands possess color patterns of Alouatta belzebul,while Alouatta seniculusis confirmed as the species that inhabits Gurupá Island. The high variability of pelage coloration of the animals from Marajó, Caviana, and Mexiana Islands includes all phenotypes formerly designated as different subspecies. The howler populations from these three islands belong to the same subspecies as those populations that inhabit the region of Tucurui dam reservoir (area 4). Finally, it seems that, as also suggested by chromosome studies, A. belzebulprobably comprises different epiphenotypes without taxonomic validity.     

Genetic structure of island and mainland populations of a Neotropical bumble bee species

As a consequence of founder effects, small population size and demographic constraints, island populations are often characterized by low genetic diversity and high inbreeding. The effects of inbreeding are more pronounced in haplo-diploid insects like bees than in similar diploid species, because their method of sex determination requires heterozygosity at a sex locus. Inbreeding leads to homozygosity at the sex locus and the production of non-viable diploid males. This means that island populations of bees are particularly prone to extinction. Here we determine the levels of diversity and isolation between islands and mainland populations of the bumble bee Bombus morio in southeast Brazil. We analyzed 659 individuals from 24 populations, sequencing two mitochondrial genes (COI and Cytb) and genotyping all individuals at 14 microsatellite loci. Surprisingly, genetic diversity was high and genetic isolation was low in all populations except Teodoro Sampaio (mainland) and Ilha da Vitória (island). Genetic diversity is not significantly correlated with island area, but is lower in populations that are more distant from the mainland. Except perhaps for Ilha da Vitória, we suggest that the island populations are unlikely to go extinct due to genetic factors. Finally, based on its genetic distance from all other populations, we identify a putative new subspecies in the Teodoro Sampaio region.     

Genetic diversity in Delphinium variegatum (Ranunculaceae): a comparison of two insular endemic subspecies and their widespread mainland relative

Delphinium variegatum is subdivided into three subspecies: D. v. variegatum is widespread in central and northern California, while D. v. kinkiense (an endangered taxon) and D. v. thornei are endemic to San Clemente Island off the coast of southern California. Electrophoretic data for 19 loci were collected from 7 populations of the mainland subspecies and all 24 known populations of the two insular endemic subspecies. Populations of the widespread mainland subspecies have more polymorphic loci (33.6% vs. 24.5%) and more alleles per polymorphic locus (2.61 vs. 2.15) than the insular endemic subspecies. However, observed heterozygosities are lower in the mainland subspecies (0.041 vs. 0.071), presumably due to lower levels of outcrossing (t = 0.464 vs. 0.895). Expected heterozygosities are similar (0.064 vs. 0.074) due to lower alternative allele frequencies in populations of the mainland subspecies (mean q = 0.075 vs. 0.190). Populations of the two insular subspecies are almost equivalent genetically (mean I = 0.997) regardless of taxonomic designation or geographic location. In contrast, one of the mainland populations is genetically well differentiated from the others. If this exceptional population is excluded, the mainland subspecies partitions genetic diversity similarly to the island subspecies, with most variation being found within populations (G(ST) = 0.073 vs. 0.030).     

Population structure of loggerhead shrikes in the California Channel Islands

The loggerhead shrike (Lanius ludovicianus), a songbird that hunts like a small raptor, maintains breeding populations on seven of the eight California Channel Islands. One of the two subspecies, L. l. anthonyi, was described as having breeding populations on six of the islands while a second subspecies, L. l. mearnsi, was described as being endemic to San Clemente Island. Previous genetic studies have demonstrated that the San Clemente Island loggerhead shrike is well differentiated genetically from both L. l. anthonyi and mainland populations, despite the fact that birds from outside the population are regular visitors to the island. Those studies, however, did not include a comparison between San Clemente Island shrikes and the breeding population on Santa Catalina Island, the closest island to San Clemente. Here we use mitochondrial control region sequences and nuclear microsatellites to investigate the population structure of loggerhead shrikes in the Channel Islands. We confirm the genetic distinctiveness of the San Clemente Island loggerhead shrike and, using Bayesian clustering analysis, demonstrate the presence and infer the source of the nonbreeding visitors. Our results indicate that Channel Island loggerhead shrikes comprise three distinct genetic clusters that inhabit: (i) San Clemente Island, (ii) Santa Catalina Island and (iii) the Northern Channel Islands and nearby mainland; they do not support a recent suggestion that all Channel Island loggerhead shrikes should be managed as a single entity.     

Biogeographical kinetics on mainland and island volcanoes

Aim To compare post‐eruption biotic recolonization times on mainland and island volcanoes. Location The research involved the study of the recolonization kinetics of Mt Vesuvius (a mainland volcano in southern Italy) and the Island of Vulcano (southern Italy). Comparisons were also made with Jorullo Volcano (Mexico) and Mount St Helens (USA) (two mainland volcanoes) and with Krakatau (Indonesia) (an island volcano). Methods Island volcanoes are expected to possess inherently impoverished faunas and floras, and recolonization after eruption is expected to occur to a low level. In comparison, the recolonization kinetics for a mainland volcano should be characterized by a higher plateau of species, and by species with low dispersal ability. To test this model, recolonization times after the small‐scale Plinian eruption of 1631 were calculated for various insect groups of Mt Vesuvius and compared with recolonization times calculated for the Island of Vulcano, which erupted dramatically in 1888. For this purpose, thorough insect checklists, based on exhaustive samplings, were extracted from the literature. Results obtained from Mt Vesuvius and Vulcano were also compared with recolonization times calculated for biotas of other mainland and island volcanoes. Results Insect recolonization times from the 1631 Vesuvius eruption varied according to the ecology of the animal group considered and appeared very long when compared with those obtained for the island volcano of Vulcano. Results obtained from Vulcano also suggest the possibility that this island hosts more species than expected at equilibrium, a state of affairs also found for the butterflies of Krakatau. Main conclusions In keeping with the predictions of multi‐phase models developed in island biogeography theory, island volcanoes have a lower species richness at equilibrium than do mainland volcanoes, but might host, in a first phase of recolonization, more species than expected at equilibrium, because ecological space is unsaturated and inter‐specific interactions are limited. The lower isolation of mainland volcanoes (allowing higher immigration rates) leads to higher rates and longer periods of recolonization and hence to higher species richness at equilibrium.     

Nestedness in island faunas: novel insights into island biogeography through butterfly community profiles of colonization ability and migration capacity

Aim To relate variation in the migration capacity and colonization ability of island communities to island geography and species island occupancy. Location Islands off mainland Britain and Ireland. Methods Mean migration (transfer) capacity and colonization (establishment) ability (ecological indices), indexed from 12 ecological variables for 56 butterfly species living on 103 islands, were related to species nestedness, island and mainland source geography and indices using linear regression models, RLQ analysis and fourth‐corner analysis. Random creation of faunas from source species, rank correlation and rank regression were used to examine differences between island and source ecological indices, and relationships to island geography. Results Island butterfly faunas are highly nested. The two ecological indices related closely to island occupancy, nestedness rank of species, island richness and geography. The key variables related to migration capacity were island area and isolation; for colonization ability they were area, isolation and longitude. Compared with colonization ability, migration capacity was found to correlate more strongly with island species occupancy and species richness. For island faunas, the means for both ecological indices decreased, and variation increased, with increasing island species richness. Mean colonization ability and migration capacity values were significantly higher for island faunas than for mainland source faunas, but these differences decreased with island latitude. Main conclusions The nested pattern of butterfly species on islands off mainland Britain and Ireland relates strongly to colonization ability but especially to migration capacity. Differences in colonization ability among species are most obvious for large, topographically varied islands. Generalists with abundant multiple resources and greater migration capacity are found on all islands, whereas specialists are restricted to large islands with varied and long‐lived biotopes, and islands close to shore. The inference is that source–sink dynamics dominate butterfly distributions on British and Irish islands; species are capable of dispersing to new areas, but, with the exception of large and northern islands, facilities (resources) for permanent colonization are limited. The pattern of colonization ability and migration capacity is likely to be repeated for mainland areas, where such indices should provide useful independent measures for assessing the conservation status of faunas within spatial units.     

Exclusion of introduced deer increases size and seed production success in an island‐endemic plant species

The presence of extra‐local invaders, such as the southern California mule deer (Odocoileus hemionus) on Santa Catalina Island, may contribute to more selective and insidious effects within the unique ecosystems that have evolved in their absence. Studies at the species level may detect effects not noticed in broader, community level vegetation monitoring or help tease apart differences in the level of effect among the various ecological components of an invaded system. In this initial study, we measured the impacts of herbivory by mule deer, a species native to analogous habitats on the adjacent mainland, on size and seed production success for Crocanthemum greenei (island rush‐rose), a federally listed sub‐shrub that is not present on mainland California. We found deer exclusion resulted in an overall increase in stem measurement of 18.8 cm. Exclosure populations exhibited complete seed production success, whereas control populations showed significantly reduced success and exhibited complete failure within 58% of populations. These results show that the introduced mule deer on Santa Catalina Island are negatively affecting a federally threatened plant species. This strongly implies that the current deer management strategy is insufficient, if one of its goals is biodiversity and endemic species conservation.     

Absence of founder effect and evidence for adaptive divergence in a recently introduced insular population of white‐tailed deer (Odocoileus virginianus)

Islands are generally colonized by few individuals which could lead to a founder effect causing loss of genetic diversity and rapid divergence by strong genetic drift. Insular conditions can also induce new selective pressures on populations. Here, we investigated the extent of genetic differentiation within a white‐tailed deer (Odocoileus virginianus) population introduced on an island and its differentiation with its source mainland population. In response to their novel environmental conditions, introduced deer changed phenotypically from mainland individuals, therefore we investigated the genetic bases of the morphological differentiation. The study was conducted on Anticosti Island (Québec, Canada) where 220 individuals were introduced 120 years ago, resulting in a population size over 160,000 individuals. We used genotyping‐by‐sequencing (GBS) to generate 8,518 filtered high‐quality SNPs and compared patterns of genetic diversity and differentiation between the continental and Anticosti Island populations. Clustering analyses indicated a single panmictic island population and no sign of isolation by distance. Our results revealed a weak, albeit highly significant, genetic differentiation between the Anticosti Island population and its source population (mean F_ST = 0.005), which allowed a population assignment success of 93%. Also, the high genetic diversity maintained in the introduced population supports the absence of a strong founder effect due to the large number of founders followed by rapid population growth. We further used a polygenic approach to assess the genetic bases of the divergent phenotypical traits between insular and continental populations. We found loci related to muscular function and lipid metabolism, which suggested that these could be involved in local adaptation on Anticosti Island. We discuss these results in a harvest management context.     

Evolutionary history of Scinax treefrogs on land‐bridge islands in south‐eastern Brazil

Aim We investigated how Pleistocene refugia and recent (c. 12,000 years ago) sea level incursions shaped genetic differentiation in mainland and island populations of the Scinax perpusillus treefrog group. Location Brazilian Atlantic Forest, São Paulo state, south‐eastern Brazil. Methods Using mitochondrial and microsatellite loci, we examined population structure and genetic diversity in three species from the S. perpusillus group, sampled from three land‐bridge islands and five mainland populations, in order to understand the roles of Pleistocene forest fragmentation and sea level incursions on genetic differentiation. We calculated metrics of relatedness and genetic diversity to assess whether island populations exhibit signatures of genetic drift and isolation. Two of the three island populations in this study have previously been described as new species based on a combination of distinct morphological and behavioural characters, thus we used the molecular datasets to determine whether phenotypic change is consistent with genetic differentiation. Results Our analyses recovered three distinct lineages or demes composed of northern mainland São Paulo populations, southern mainland São Paulo populations, and one divergent island population. The two remaining island populations clustered with samples from adjacent mainland populations. Estimates of allelic richness were significantly lower, and estimates of relatedness were significantly higher, in island populations relative to their mainland counterparts. Main conclusions Fine‐scale genetic structure across mainland populations indicates the possible existence of local refugia within São Paulo state, underscoring the small geographic scale at which populations diverge in this species‐rich region of the Atlantic Coastal Forest. Variation in genetic signatures across the three islands indicates that the populations experienced different demographic processes after marine incursions fragmented the distribution of the S. perpusillus group. Genetic signatures of inbreeding and drift in some island populations indicate that small population sizes, coupled with strong ecological selection, may be important evolutionary forces driving speciation on land‐bridge islands.     

Genetic differences between the endangered San Clemente Island loggerhead shrike Lanius ludovicianus mearnsi and two neighbouring subspecies demonstrated by mtDNA control region and cytochrome b sequence variation

We investigated mtDNA sequence variation in five populations of the loggerhead shrike Lanius ludovicianus , representing four subspecies, including the San Clemente loggerhead shrike L. l. mearnsi , a critically endangered California Channel Island endemic. Variability in 200 bp of control region and 200 bp of cytochrome b was extremely low, and defined four haplotypes. Strong structure was apparent among all three southern Californian subspecies, including L. l. mearnsi , with one haplotype predominating in each subspecies. Although potential levels of gene flow between L. l. mearnsi and neighbouring populations are low, mtDNA data support field observations that some shrikes visit the island during winter but do not stay to breed, and suggest that these birds come from the mainland. The similarity in haplotypes between populations from Saskatchewan, Canada and those in southern California suggests post-glacial northern range expansion of the species. Our results confirm the evolutionary distinctiveness of L. l. mearnsi and justify continuing efforts for its conservation.