Mainland Populations Research Articles

Vicariance and ecological adaptation drive genetic and morphological diversification of a widely distributed bug, Carbula crassiventris (Insecta: Hemiptera: Pentatomidae), in South China

1. Vicariance and ecological adaptation are two evolutionary mechanisms that can generate biodiversity. Evidence from recent studies has shown that the patterns of genetic variation of species distributed in South China are influenced by the Taiwan Strait and/or the Qinghai‐Tibet Plateau (QTP).2. This study sequenced three mitochondrial and one nuclear genes from 174 individuals Carbula crassiventris and conducted phylogenetic and phylogeographical analyses, asymmetric gene flow estimation, intraspecific divergence time and historical demographic reconstruction, morphological comparison, ecological niche modelling (ENM), and isolation‐by‐distance (IBD) and isolation‐by‐environment (IBE) modelling to test if vicariance and ecological adaptation jointly affected biogeographic patterns in South China.3. According to the results of phylogenetic and phylogeographical analyses, C. crassiventris was divided into three populations (Mainland, Xizang, and Taiwan). Asymmetric gene flows were detected from the Mainland to Xizang populations and from the Mainland to Taiwan populations. Morphological comparison showed that the individuals from the three defined populations have significant differences in four variables. The ENM results suggested that suitable habitat has expanded from the Last Glacial Maximum to the present. Partial Mantel tests indicated that individuals in the Mainland population were not dispersal‐limited, regardless of geographic or environmental distance, but that a significant IBE relationship was present in the Mainland–Xizang lineage. When including the Taiwan population in the dataset, significant IBD and IBE relationships were detected.4. This study revealed that both vicariance, with the Taiwan Strait as a geographical barrier, and ecological adaptation, in both the QTP and Taiwan, jointly influence population divergence of C. crassiventris.

Dispersal ability predicts spatial genetic structure in native mammals persisting across an urbanization gradient.

As the rate of urbanization continues to increase globally, a growing body of research is emerging that investigates how urbanization shapes the movement—and consequent gene flow—of species in cities. Of particular interest are native species that persist in cities, either as small relict populations or as larger populations of synanthropic species that thrive alongside humans in new urban environments. In this study, we used genomic sequence data (SNPs) and spatially explicit individual‐based analyses to directly compare the genetic structure and patterns of gene flow in two small mammals with different dispersal abilities that occupy the same urbanized landscape to evaluate how mobility impacts genetic connectivity. We collected 215 white‐footed mice (Peromyscus leucopus) and 380 big brown bats (Eptesicus fuscus) across an urban‐to‐rural gradient within the Providence, Rhode Island (U.S.A.) metropolitan area (population =1,600,000 people). We found that mice and bats exhibit clear differences in their spatial genetic structure that are consistent with their dispersal abilities, with urbanization having a stronger effect on Peromyscus mice. There were sharp breaks in the genetic structure of mice within the Providence urban core, as well as reduced rates of migration and an increase in inbreeding with more urbanization. In contrast, bats showed very weak genetic structuring across the entire study area, suggesting a near‐panmictic gene pool likely due to the ability to disperse by flight. Genetic diversity remained stable for both species across the study region. Mice also exhibited a stronger reduction in gene flow between island and mainland populations than bats. This study represents one of the first to directly compare multiple species within the same urban‐to‐rural landscape gradient, an important gap to fill for urban ecology and evolution. Moreover, here we document the impacts of dispersal capacity on connectivity for native species that have persisted as the urban landscape matrix expands.

Association of rare heterozygous PLA2G6 variants with the risk of Parkinson's disease

The PLA2G6 gene has been identified as a causative gene for autosomal recessive early-onset dystonia-parkinsonism. Possible association was reported between single heterozygous PLA2G6 mutation and the risk of Parkinson's disease (PD), which, however, remained inconclusive. To clarify the effect of heterozygous PLA2G6 variants on the risk of PD, a total of 3710 patients with PD and 2636 controls of Chinese mainland population were recruited and genotyped by whole-exome sequencing or whole-genome sequencing. Variants in the PLA2G6 coding region were extracted and subjected to burden analysis using the optimal sequence kernel association test. In total, we identified 86 rare heterozygous variants in the PLA2G6 coding region, whereas no significant difference was found between cases and controls. Therefore, we found no supportive evidence for heterozygous PLA2G6 variants being a risk factor for PD in Chinese mainland population.

Conspecific and Predator Perception of the Red Oophaga pumilio Morph from the Central Caribbean of Costa Rica

Strawberry Poison Frogs (Oophaga pumilio) are common members of leaf litter lowland communities in Central America and exhibit several color morphs throughout their distribution. Color plays a determinant role during intra- and intermorph interactions in many insular populations, but little is known about the variation and perception of visual signals in mainland populations. In this study, we investigated color variation of four body parts—head, back, belly, and throat—in a bright red O. pumilio population of northeastern Costa Rica. We incorporated frog- and bird-specific visual modeling to evaluate the differences in color and brightness between the sexes, from the perspective of conspecifics and avian predators. Furthermore, we measured the color and brightness contrast against natural backgrounds commonly used by these frogs to forage and patrol within territories. Our results revealed that, from the perspective of conspecifics, there is no dichromatism between males and females. However, females had a greater contrast against green and brown backgrounds than males. The bird visual models indicated that males and females are highly conspicuous against common background substrates but that females are easier to detect than males. This study detailing color variants between sexes within a mainland population of O. pumilio contributes to our understanding of color differences in populations of this species.

Morphological divergence in giant fossil dormice.

Insular gigantism-evolutionary increases in body size from small-bodied mainland ancestors-is a conceptually significant, but poorly studied, evolutionary phenomenon. Gigantism is widespread on Mediterranean islands, particularly among fossil and extant dormice. These include an extant giant population of Eliomys quercinus on Formentera, the giant Balearic genus †Hypnomys and the exceptionally large †Leithia melitensis of Pleistocene Sicily. We quantified patterns of cranial and mandibular shape and their relationships to head size (allometry) among mainland and insular dormouse populations, asking to what extent the morphology of island giants is explained by allometry. We find that gigantism in dormice is not simply an extrapolation of the allometric trajectory of their mainland relatives. Instead, a large portion of their distinctive cranial and mandibular morphology resulted from the population- or species-specific evolutionary shape changes. Our findings suggest that body size increases in insular giant dormice were accompanied by the evolutionary divergence of feeding adaptations. This complements other evidence of ecological divergence in these taxa, which span predominantly faunivorous to herbivorous diets. Our findings suggest that insular gigantism involves context-dependent phenotypic modifications, underscoring the highly distinctive nature of island faunas.

Selection underlies phenotypic divergence in the insular Azores woodpigeon

AbstractThe study of phenotypic evolution in island birds following colonization is a classic topic in island biogeography. However, few studies explicitly test for the role of selection in shaping trait evolution in these taxa. Here, we studied the Azores woodpigeon (Columba palumbus azorica) to investigate differences between island and mainland populations, between females and males, and interactions between geographical origin and sex, by using spectrophotometry to quantify plumage colour and linear measurements to examine external and skeletal morphology. We further tested if selection explains the observed patterns by comparing phenotypic differentiation to genome‐wide neutral differentiation. Our findings are consistent with several predictions of morphological evolution in island birds, namely differences in bill, flight and leg morphology and coloration differences between island and mainland birds. Interestingly, some plumage and morphological traits that differ between females and males respond differently according to geographical origin. Sexual dimorphism in colour saturation is more pronounced in the mainland, but this is driven by selection on female plumage coloration. Differences in flight morphology between females and males are also more pronounced in the mainland, possibly to accommodate contrasting pressures between migration and flight displays. Overall, our results suggest that phenotypic differentiation between mainland and island populations leading to divergent sexual dimorphism patterns can arise from selection acting on both females and males on traits that are likely under the influence of natural and sexual selection.

Population structure of a nest parasite of Darwin’s finches within its native and invasive ranges

Invasive species are one of the greatest threats to biodiversity, with endemic species on islands being at particular risk. Management programs can help to minimize these impacts, but such programs are most successful when they are well-informed. In the Galapagos Islands, Ecuador, a recently introduced avian parasitic fly, Philornis downsi, has had strong negative effects on the survival of multiple endemic bird species, including several species of Darwin’s finches. The fly now populates most of the major islands within the Archipelago and the need to better understand the population structure and connectivity patterns of this invasive fly has become increasingly apparent as various management efforts are being considered. Here, we use genomic and phylogenetic approaches to estimate population structure and connectivity for P. downsi collected from five islands within the Galapagos Islands and several sites in mainland Ecuador, which is the presumptive origin of the invasive population. Genomic data showed very little genetic differentiation between island populations of P. downsi relative to the mainland. Phylogenetic analyses, which used more conservative genetic markers than the genomics approach, showed that island and mainland populations of flies were highly related. Our study provides some of the first results using genetic data to quantify differentiation among mainland and island populations of P. downsi. In addition, our study found very little genetic differentiation between island populations of flies, suggesting that there may be considerable gene flow among islands; however, further sampling is needed to determine the extent to which this could be occurring. As management techniques aimed at controlling the impact of this parasite on endemic bird populations are being considered, our study provides important insights into the history of P. downsi’s invasion to the Galapagos Islands and current population connectivity patterns.

Scale-dependent effects of habitat fragmentation on the genetic diversity of Actinidia chinensis populations in China

Spatial scale partly explains the differentiated effects of habitat fragmentation on plant biodiversity, but the mechanisms remain unclear. To investigate the effects of habitat fragmentation on genetic diversity at different scales, we sampled Actinidia chinensis Planch. at broad and fine scales, China. The broad-scale sampling included five mountain populations and one oceanic island population (Zhoushan Archipelago), and the fine-scale sampling covered 11 lake islands and three neighboring land populations in Thousand-Island Lake (TIL). These populations were genotyped at 30 microsatellite loci, and genetic diversity, gene flow, and genetic differentiation were evaluated. Genetic differentiation was positively related to geographical distance at the broad scale, indicating an isolation-by-distance effect of habitat fragmentation on genetic diversity. The oceanic population differed from the mainland populations and experienced recent bottleneck events, but it showed high gene flow with low genetic differentiation from a mountain population connected by the Yangtze River. At the fine scale, no negative genetic effects of habitat fragmentation were found because seed dispersal with water facilitates gene flow between islands. The population size of A. chinensis was positively correlated with the area of TIL islands, supporting island biogeography theory, but no correlation was found between genetic diversity and island area. Our results highlight the scale-dependent effects of habitat fragmentation on genetic diversity and the importance of connectivity between island-like isolated habitats at both the broad and fine scales.

A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae)

We review the species of Bidessus of Madagascar and describe Bidessus anjozorobe sp. nov. from material collected in Anjozorobe forest. Anjozorobe is part of the Anjozorobe-Angavo Protected Area, which is an important corridor of transition forest between typical eastern humid forests and the residual sub-humid forest of the Central Highlands. Bidessus longistriga Régimbart, 1895 and Bidessus perexiguus Kolbe, 1883 are widespread but endemic low-altitude species on Madagascar. Bidessus nesioticus Guignot, 1956 is an alpine species described from near the peak of the Ankaratra mountain massifs at 2500 m a.s.l. We recollected the species for the first time since its description, in Ankaratra and in a new area above 2000 m a.s.l. in the Andringitra mountain further south. Bidessus cf. nero Gschwendtner, 1933 is tentatively recorded for Madagascar for the first time but further studies are needed to test the status of mainland and insular populations. Bidessus apicidens Biström & Sanfilippo, 1986 has not been recollected on Madagascar since 1970. All species are endemic to Madagascar except potentially Bidessus cf. ceratus and Bidessus cf. nero described from Uganda and the Democratic Republic of the Congo, respectively. The older records of the two non-endemic species Bidessus complicatus Sharp, 1904 and Bidessus ovoideus Régimbart, 1895 on Madagascar could not be verified.

The ghost of connections past: A role for mainland vicariance in the isolation of an insular population of the red‐billed chough (Aves: Corvidae)

AbstractAimOceanic islands have often been colonized by small groups of individuals dispersing from the nearest mainland, giving rise to insular populations characterized by locally adapted phenotypes and low genetic diversity. Alternatively, due to past geo‐climatic changes, the present‐day distribution of the species may not correspond to that found at the time of the original colonization so that the current mainland distribution may not include the original source area, leading to erroneous assumptions regarding colonization history. Here, we use patterns of genetic variation to evaluate alternative colonization scenarios of an insular passerine in the Canary Islands.LocationLa Palma (Canary Islands), Northern Africa and the Iberian Peninsula.TaxonRed‐billed chough (Pyrrhocorax pyrrhocorax).MethodsWe use phylogeographical and coalescent analyses of mitochondrial DNA sequences and 10 microsatellite loci, together with Bayesian demographic modelling, to determine whether choughs on the island of La Palma originate from (a) present‐day populations in Iberia, (b) present‐day populations in the mountains of inland Morocco or (c) former populations in coastal Morocco, where suitable habitat existed in the past.ResultsBoth the mitochondrial and nuclear datasets indicate that the chough population on La Palma is genetically well differentiated from those in Iberia and Morocco, and that La Palma choughs are more closely related to choughs in Iberia than to those in Morocco. Genetic diversity in La Palma is lower than that of mainland populations, but shows no evidence of past bottlenecks. The best supported demographic model to explain the origin of La Palma choughs that is congruent with both genetic datasets includes a ‘ghost’ population closely related to Iberia, from which the insular population diverged within the last 30,000 years.Main conclusionsOur results are most consistent with the existence of a former connection between La Palma and Iberia along the North African coast, when suitable habitat was found there. Subsequent desertification of these coastal areas led to local extinctions that restricted gene flow between Iberia and the islands, promoting genetic differentiation. Our results provide a counterintuitive solution to a biogeographical enigma, and could help resolve the colonization history of other systems with similarly complex climatic pasts.

Leaf functional traits and insular colonization: Subtropical islands as a melting pot of trait diversity in a widespread plant lineage

AbstractAimOne of the main goals of functional biogeography is to examine distribution patterns of trait diversity, and islands provide excellent study cases for this emerging field. We tested the hypothesis that multiple dispersals from a common mainland pool would promote functional similarity among island systems when environmental conditions are similar, but also novel phenotypic traits related to colonization history and exploitation of new habitats.LocationMediterranean Basin and Macaronesian islands.TaxonWolfbane (Periploca laevigata)MethodsWe used the well‐known biogeographical history of a woody plant complex (P. laevigata s.l.) to examine trait variation and how it relates to climatic conditions of mainland and subtropical island settings. In a common garden experiment, we measured a suite of leaf physiological and anatomical traits tightly related to plant performance in 320 seedlings representing 21 populations of five sublineages—the oldest (2.6 my) island colonization (western Canary Islands) as a reference, three sublineages stemming from independent events of island colonization in the last 0.5 my from NW Africa (Cape Verde, Fuerteventura, Lanzarote) and their widespread Mediterranean mainland counterpart.ResultsWe observed strong phenotypic divergence between island and mainland sublineages linked to contrasting climatic conditions. Mediterranean mainland populations displayed a very specialized leaf phenotype characteristic of arid plants (i.e. small leaves, amphistomaty, isobilateral mesophyll, high photosynthetic rates). In turn, low seasonality on islands was linked to the recurrent expression of a phenotype characterized by larger leaves and lower photosynthetic rates. Our analyses showed that the high investment in secondary compounds (i.e. tannins) on islands decouples photosynthesis from growth rates. Despite this pattern of parallel differentiation, each island sublineage displayed a distinctive phenotype, with some traits related to colonization time, which resulted in a mosaic of functional variation across island systems.Main conclusionsOur data suggest that the studied subtropical islands promote expression of traits specific to certain sublineages and other common traits that are no longer adaptive in the original mainland pool due to Pleistocene climatic shifts. These findings ultimately extend the role of islands as biodiversity refugia and hotspots of plant functional diversity.

Prion Protein Gene (PRNP) Sequences Suggest Differing Vulnerability to Chronic Wasting Disease for Florida Key Deer (Odocoileus virginianus clavium) and Columbian White-Tailed Deer (O. v. leucurus).

Chronic wasting disease (CWD) is a fatal, highly transmissible spongiform encephalopathy caused by an infectious prion protein. CWD is spreading across North American cervids. Studies of the prion protein gene (PRNP) in white-tailed deer (WTD; Odocoileus virginianus) have identified non-synonymous substitutions associated with reduced CWD frequency. Because CWD is spreading rapidly geographically, it may impact cervids of conservation concern. Here, we examined the genetic vulnerability to CWD of 2 subspecies of WTD: the endangered Florida Key deer (O. v. clavium) and the threatened Columbian WTD (O. v. leucurus). In Key deer (n = 48), we identified 3 haplotypes formed by 5 polymorphisms, of which 2 were non-synonymous. The polymorphism c.574G>A, unique to Key deer (29 of 96 chromosomes), encodes a non-synonymous substitution from valine to isoleucine at codon 192. In 91 of 96 chromosomes, Key deer carried c.286G>A (G96S), previously associated with substantially reduced susceptibility to CWD. Key deer may be less genetically susceptible to CWD than many mainland WTD populations. In Columbian WTD (n = 13), 2 haplotypes separated by one synonymous substitution (c.438C>T) were identified. All of the Columbian WTD carried alleles that in other mainland populations are associated with relatively high susceptibility to CWD. While larger sampling is needed, future management plans should consider that Columbian WTD are likely to be genetically more vulnerable to CWD than many other WTD populations. Finally, we suggest that genetic vulnerability to CWD be assessed by sequencing PRNP across other endangered cervids, both wild and in captive breeding facilities.

Population Divergence along a Genetic Line of Least Resistance in the Tree Species Eucalyptus globulus.

The evolutionary response to selection depends on the distribution of genetic variation in traits under selection within populations, as defined by the additive genetic variance-covariance matrix (G). The structure and evolutionary stability of G will thus influence the course of phenotypic evolution. However, there are few studies assessing the stability of G and its relationship with population divergence within foundation tree species. We compared the G-matrices of Mainland and Island population groups of the forest tree Eucalyptus globulus, and determined the extent to which population divergence aligned with within-population genetic (co)variation. Four key wood property traits exhibiting signals of divergent selection were studied—wood density, extractive content, and lignin content and composition. The comparison of G-matrices of the mainland and island populations indicated that the G-eigenstructure was relatively well preserved at an intra-specific level. Population divergence tended to occur along a major direction of genetic variation in G. The observed conservatism of G, the moderate evolutionary timescale, and close relationship between genetic architecture and population trajectories suggest that genetic constraints may have influenced the evolution and diversification of the E. globulus populations for the traits studied. However, alternative scenarios, including selection aligning genetic architecture and population divergence, are discussed.

In situ glacial survival maintains high genetic diversity of Mussaenda kwangtungensis on continental islands in subtropical China.

Generally, island populations are predicted to have less genetic variation than their mainland relatives. However, a growing number of studies have nevertheless reported exceptions, indicating that the relationships were impacted by several factors, for example, historical processes. In the present study, we chose a group of subtropical islands located in South China as the study system, which are quite younger and much closer to the mainland than most of the previous studied island systems, to test the hypothesis that in situ glacial survival contributes to high levels of genetic diversity in island populations. We conducted a comparison of genetic variation between 12 island and 11 nearby mainland populations of Mussaenda kwangtungensis using eleven nuclear microsatellite and three chloroplast markers, evaluated effects of the island area and distance to mainland on genetic diversity of island populations, and simulated the potential distribution over the past by ecological niche modeling, together with the genetic data to detect the role of islands during the glacial periods. The island populations displayed comparable levels of genetic diversity and differentiation with mainland populations, overall high levels of unique polymorphisms, and the greatest values of specific within‐population genetic diversity. No significant correlation was detected between genetic diversity of island populations and distance to mainland, as well as area of islands, except that allelic richness was significantly positively correlated with the area of islands. Nuclear microsatellites revealed two main clusters, largely corresponding to islands and inland populations, which divergence dated to a time of island formation by ABC analysis. Ecological niche modeling predicted a highly climatic suitability on islands during the last glacial maximum (LGM). Our results suggest that the islands have acted as refugia during the LGM and highlight the role of in situ glacial survival in maintaining high levels of genetic diversity of M. kwangtungensis in continental islands of subtropical China.

Rapid Dietary Shift in Podarcis siculus Resulted in Localized Changes in Gut Function.

AbstractNatural dietary shifts offer the opportunity to address the nutritional physiological characters required to thrive on a particular diet. Here, we studied the nutritional physiology of Podarcis siculus, with populations on Pod Mrčaru, Croatia, that have become omnivorous and morphologically distinct (including the development of valves in the hindgut) from their insectivorous source population on Pod Kopište. We compared gut structure and function between the two island populations of this lizard species and contrasted them with an insectivorous mainland out-group population in Zagreb. On the basis of the adaptive modulation hypothesis, we predicted changes in gut size and structure, digestive enzyme activities, microbial fermentation products (short-chain fatty acids [SCFAs]), and plant material digestibility concomitant with this dietary change. The Pod Mrčaru population had heavier guts than the mainland population, but there were no other differences in gut structure. Most of the enzymatic differences we detected were between the island populations and the out-group population. The Pod Mrčaru lizards had higher amylase and trehalase activities in their hindguts compared with the Pod Kopište population, and the Pod Kopište lizards had greater SCFA concentrations in their hindguts than the omnivorous Pod Mrčaru population. Interestingly, the differences between the Pod Mrčaru and Pod Kopište populations are primarily localized to the hindgut and are likely influenced by microbial communities and a higher food intake by the Pod Mrčaru lizards. Although subtle, the changes in hindgut digestive physiology impact the digestibility of plant material in adult lizards-Pod Mrčaru lizards had higher digestibility of herbivorous and omnivorous diets fed over several weeks in the laboratory than did their source population.

Skull shape of a widely distributed, endangered marsupial reveals little evidence of local adaptation between fragmented populations.

The biogeographic distribution of diversity among populations of threatened mammalian species is generally investigated using population genetics. However, intraspecific phenotypic diversity is rarely assessed beyond taxonomy‐focused linear measurements or qualitative descriptions. Here, we use a technique widely used in the evolutionary sciences—geometric morphometrics—to characterize shape diversity in the skull of an endangered marsupial, the northern quoll, across its 5,000 km distribution range along Northern Australia. Skull shape is a proxy for feeding, behavior, and phenotypic differentiation, allowing us to ask whether populations can be distinguished and whether patterns of variation indicate adaptability to changing environmental conditions. We analyzed skull shape in 101 individuals across four mainland populations and several islands. We assessed the contribution of population, size, sex, rainfall, temperature, and geography to skull shape variation using principal component analysis, Procrustes ANOVA, and variation partitioning analyses. The populations harbor similar amounts of broadly overlapping skull shape variation, with relatively low geographic effects. Size predicted skull shape best, coinciding with braincase size variation and differences in zygomatic arches. Size‐adjusted differences in populations explained less variation with far smaller effect sizes, relating to changes in the insertion areas of masticatory muscles, as well as the upper muzzle and incisor region. Climatic and geographic variables contributed little. Strikingly, the vast majority of shape variation—76%—remained unexplained. Our results suggest a uniform intraspecific scope for shape variation, possibly due to allometric constraints or phenotypic plasticity beyond the relatively strong allometric effect. The lack of local adaptation indicates that cross‐breeding between populations will not reduce local morphological skull (and probably general musculoskeletal) adaptation because none exists. However, the potential for heritable morphological variation (e.g., specialization to local diets) seems exceedingly limited. We conclude that 3D geometric morphometrics can provide a comprehensive, statistically rigorous phenomic contribution to genetic‐based conservation studies.

Island invasion and reinvasion: Informing invasive species management with genetic measures of connectivity

Abstract Invasive species are the major threat to island biodiversity world‐wide. Genetic analyses assist in identifying invasion routes as well as revealing population connectivity, which both represent crucial information for conservation management strategies and risk evaluation. Such information is critical to safeguarding vulnerable species on nearshore islands, which often serve as wildlife sanctuaries. The house mouse Mus musculus has invaded islands around the world and is a model species for showcasing how genetic tools can be used to inform biosecurity management. The genetic population structure of 316 mice from 12 locations in the upper South Island of New Zealand was determined, using novel GenePlots and traditional population genetic tools based on 10 microsatellite loci, to identify gene flow and reinvasion pathways among mainland and island populations over a decade. On the mainland, populations remained genetically homogeneous over landscape scales of many tens of kilometres. In contrast, historically established island populations only kilometres offshore had low genetic diversity from prolonged isolation. Two islands were potentially colonized from both the mainland and each other in a hybrid swarm. Islands that had recently been invaded or reinvaded in the past decade had genetic profiles consistent with the adjacent mainland, suggesting failure of biosecurity procedures to prevent reinvasion, rather than eradication survivors. Although two islands were invaded by only a few individuals, on a third island many invaders simultaneously arrived. Synthesis and applications. Assessing the genetic structure and connectivity of mainland and island populations of an invasive species, using a combination of traditional and novel visualization tools, has uncovered a spectrum of invasion mechanisms and pathways. These results have informed ongoing biosecurity measures by revealing the locations and intensities of biosecurity threats, allowing targeted management actions to reduce the likelihood of island reinvasion.

Genomic diversity and population structure of the indigenous Greek and Cypriot cattle populations

BackgroundThe indigenous cattle populations from Greece and Cyprus have decreased to small numbers and are currently at risk of extinction due to socio-economic reasons, geographic isolation and crossbreeding with commercial breeds. This study represents the first comprehensive genome-wide analysis of 10 indigenous cattle populations from continental Greece and the Greek islands, and one from Cyprus, and compares them with 104 international breeds using more than 46,000 single nucleotide polymorphisms (SNPs).ResultsWe estimated several parameters of genetic diversity (e.g. heterozygosity and allelic diversity) that indicated a severe loss of genetic diversity for the island populations compared to the mainland populations, which is mainly due to the declining size of their population in recent years and subsequent inbreeding. This high inbreeding status also resulted in higher genetic differentiation within the Greek and Cyprus cattle group compared to the remaining geographical breed groups. Supervised and unsupervised cluster analyses revealed that the phylogenetic patterns in the indigenous Greek breeds were consistent with their geographical origin and historical information regarding crosses with breeds of Anatolian or Balkan origin. Cyprus cattle showed a relatively high indicine ancestry. Greek island populations are placed close to the root of the tree as defined by Gir and the outgroup Yak, whereas the mainland breeds share a common historical origin with Buša. Unsupervised clustering and D-statistics analyses provided strong support for Bos indicus introgression in almost all the investigated local cattle breeds along the route from Anatolia up to the southern foothills of the Alps, as well as in most cattle breeds along the Apennine peninsula to the southern foothills of the Alps.ConclusionsAll investigated Cyprus and Greek breeds present complex mosaic genomes as a result of historical and recent admixture events between neighbor and well-separated breeds. While the contribution of some mainland breeds to the genetic diversity pool seems important, some island and fragmented mainland breeds suffer from a severe decline of population size and loss of alleles due to genetic drift. Conservation programs that are a compromise between what is feasible and what is desirable should focus not only on the still highly diverse mainland breeds but also promote and explore the conservation possibilities for island breeds.

Long term effects of outbreeding: experimental founding of island population eliminates malformations and improves hatching success in sand lizards

Loss of genetic variation is an increasing problem in many natural populations as a result of population fragmentation, inbreeding, and genetic drift, which may lead to inbreeding depression and subsequent “extinction vortices”. In such cases, outbreeding offers a potential population saviour from extinction. Here we compare offspring viability between an experimentally founded outbred island population of sand lizards Lacerta agilis, and an inbred mainland source population on the Swedish West coast. We have studied the mainland population for over a decade during which >4000 offspring from >500 parents were monitored. We conducted an outbreeding experiment in which lizards from the mainland population with relatively low genetic variation were crossbred with lizards from distant populations that lack gene flow. The resulting 454 offspring were introduced to an otherwise uninhabited island with ideal sand lizard habitat. A survey of the island two decades later showed that offspring produced by females from the experimentally founded population had 13% higher hatching success (99.3% versus 86.4%) and elimination of the malformations occurring in 21% of clutches in the mainland source population. These results co-occur with higher genetic diversity. We conclude that outbreeding improved offspring viability in our island population ca 5–6 generations after the founding event, that is, with sustained viability effects at a time when heterotic effects are expected to have subsided.

Population genetic structure of estuary perch (Percalates colonorum Gunther) in south-eastern Australia

Estuary perch (Percalates colonorum Gunther) is an estuary dependent fish native to south-eastern Australia that is in decline. There is an increasing emphasis on stocking the species. Understanding the genetic structure across its range is important for guiding optimal stocking strategies. A prior study found some evidence of population genetic structure; however, few genetic markers were used in that assessment. Here, we develop 21 novel polymorphic microsatellite markers to reassess population genetics. Analyses indicate three broad genetic clusters, with populations on mainland Australia exhibiting an isolation by distance pattern. The only known population from Tasmania is genetically and geographically isolated from mainland populations and has very low levels of genetic diversity. We provide recommendations for sourcing broodstock from mainland populations, including describing three broad areas for procuring and releasing broodstock and offspring. The markers and results reported here will prove invaluable for guiding and monitoring the outcomes of stocking and conservation activities.