Habitat use and behavioural ecology of the juveniles of two sympatric damselfishes (Actinopterygii: Pomacentridae) in the south-western Atlantic Ocean

Spatial distribution, microhabitat use and territorial and feeding behaviours were compared between the juveniles of two sympatric territorial damselfishes Stegastes variabilis and Stegastes fuscus on a small tropical reef in the south-western Atlantic Ocean. Juvenile S. variabilis were most abundant at sites subject to stronger hydrodynamics and with mixed benthic cover, whereas juvenile S. fuscus were most abundant at sheltered sites with dense turf algae cover. No differences regarding feeding habits were detected, with both species preferentially feeding on turf algae. Also, despite similarities in territory area and agonistic encounter rates, the identity and proportion of intruders involved in agonistic interactions differed significantly between species. These interdependent traits suggest strong asymmetric competition, with juvenile S. fuscus dominating high-quality sites and evicting juvenile S. variabilis to low quality, marginal areas of the reef.     

The fishes of Saint Paul's Rocks

Fifty species of fishes are recorded from Saint Paul's Rocks in a checklist which includes notes on ecology and behaviour. The poor species diversity, which is the lowest of any tropical island studied to date, seems to result from the isolation of the Rocks and also their small size and lack of habitat diversity. Large pelagic and semi-pelagic predators, especially Galapagos sharks, are unusually common; 12.1% of identified shore fishes at St Paul's appear to be endemic to the Rocks, while 6.1% are known only from the tropical islands of the mid-Atlantic ridge (St Paul's, Ascension, St Helena); 15.2% are recorded only from Brazil and St Paul's 30.3% are widespread western Atlantic forms that have the central Atlantic as the eastern limit of their range; a further 36.4% are widely distributed throughout the tropical Atlantic. Three new species are described: Anthias salmopunctatus, Stegastes sanctipauli and Enneanectes smithi .     

Passive rafting is a powerful driver of transoceanic gene flow

Dispersal by passive oceanic rafting is considered important for the assembly of biotic communities on islands. However, not much is known about levels of population genetic connectivity maintained by rafting over transoceanic distances. We assess the evolutionary impact of kelp-rafting by estimating population genetic differentiation in three kelp-associated invertebrate species across a system of islands isolated by oceanic gaps for over 5 million years, using mtDNA and AFLP markers. The species occur throughout New Zealand''s subantarctic islands, but lack pelagic stages and any opportunity for anthropogenic transportation, and hence must rely on passive rafting for long-distance dispersal. They all have been directly observed to survive transoceanic kelp-rafting journeys in this region. Our analyses indicate that regular gene flow occurs among populations of all three species between all of the islands, especially those on either side of the subtropical front oceanographic boundary. Notwithstanding its perceived sporadic nature, long-distance kelp-rafting appears to enable significant gene flow among island populations separated by hundreds of kilometres of open ocean.     

Vicariance and marine migration in continental island populations of a frog endemic to the Atlantic Coastal forest

The theory of island biogeography is most often studied in the context of oceanic islands where all island inhabitants are descendants from founding events involving migration from mainland source populations. Far fewer studies have considered predictions of island biogeography in the case of continental islands, where island formation typically splits continuous populations and thus vicariance also contributes to the diversity of island populations. We examined one such case on continental islands in southeastern Brazil, to determine how classic island biogeography predictions and past vicariance explain the population genetic diversity of Thoropa taophora, a frog endemic to the Atlantic Coastal Forest. We used nuclear microsatellite markers to examine the genetic diversity of coastal and island populations of this species. We found that island isolation has a role in shaping the genetic diversity of continental island species, with island populations being significantly less diverse than coastal populations. However, area of the island and distance from coast had no significant effect on genetic diversity. We also found no significant differences between migration among coastal populations and migration to and from islands. We discuss how vicariance and the effects of continued migration between coastal and island populations interact to shape evolutionary patterns on continental islands.     

Evidence of connectivity between continental and differentiated insular populations in a highly mobile species

Aim Genetically differentiated insular populations are candidates for independent units for conservation. However, occasional immigration to reduced island populations may occur and potentially have important consequences in their future viability and evolutionary potential. In this study, we investigate the conservation implications of population structure and connectivity of insular and continental populations of a migratory raptor as determined using genetic tools and satellite tracking. Location Western European populations in the Iberian Peninsula and two insular populations in the Mediterranean Sea (Balearic Islands) and Atlantic Ocean (Canary Islands). Methods We genotyped 22 microsatellite loci in 96 Egyptian vultures (Neophron percnopterus) from the Iberian Peninsula, 36 from Menorca (Balearic archipelago) and 242 (85% of the current population) from Fuerteventura (Canary Islands). We analysed genetic variation to estimate structure, gene flow, genetic diversity, effective size and recent demographic history of the populations. Additionally, 19 vultures were marked with satellite transmitters to track their migration routes. Results Insular populations were genetically differentiated from those of the mainland. We detected immigration in the insular populations and within the continental counterpart. We found similar levels of genetic variability between the continent and the islands, and a bottleneck analysis indicated recent sharp population declines in both archipelagos but not on the continent. Main conclusions Our study provides evidence that, in spite of significant differentiation, insular populations of highly mobile species may remain connected with the mainland. Conservation programmes should take into account population connectivity and integrate differentiated units of management within complex units of conservation that can best maintain processes and potential for evolutionary change.     

Territorial defence by the Brazilian damsel Stegastes fuscus (Teleostei: Pomacentridae)

Territorial defence by Brazilian damselfish Stegastes fuscus was studied in north-east Brazil through underwater observations. The fish mostly fed on Gellidium sp. and strongly defended a territory with a mean size of 2 m² (range 1·27–3·07 m²); its mean ± s.d. feeding rate was 8·73 ± 2·44 bites min⁻¹. Stegastes fuscus responded similarly to all intruding fish species, with aggressive behaviour becoming more pronounced only with an increase in the number of fishes in the sampled area. Analysis of attacks elicited by different fish species placed within S. fuscus ' territory, however, showed that it launched more attacks on conspecifics than on other fishes.     

Multilocus approach reveals an incipient differentiation process in the Stone-curlew, <Emphasis Type="Italic">Burhinus oedicnemus</Emphasis> around the Mediterranean basin

The Stone-curlew Burhinus oedicnemus, a steppe bird species, is mainly distributed in the Mediterranean and Macaronesian regions, which are considered hotspots of biodiversity with priority for animal and plant species richness conservation. In this study, we investigated the genetic diversity of the Stone-curlew in the Mediterranean basin and in the Canary Islands by applying a multilocus approach. We analysed mitochondrial and nuclear markers in order to evaluate the genetic structure and the congruence between morphological subspecies and geographic samples. We found a significant level of genetic differentiation between Mediterranean and Canary Island populations with all markers. Both in the Mediterranean basin and in the Canary Islands, we found a significant level of genetic diversity with nuclear markers only. We identified seven population groups, including insular populations. The four subspecies described for the Western Palaearctic were confirmed with some changes in distribution range. In spite of habitat fragmentation and negative population trend, the Stone-curlew showed a significant level of genetic diversity and gene flow among continental populations. However, islands constitute important reservoirs of genetic diversity and a potential for the evolution of the species.     

Population size and time since island isolation determine genetic diversity loss in insular frog populations

Understanding the factors that contribute to loss of genetic diversity in fragmented populations is crucial for conservation measurements. Land‐bridge archipelagoes offer ideal model systems for identifying the long‐term effects of these factors on genetic variations in wild populations. In this study, we used nine microsatellite markers to quantify genetic diversity and differentiation of 810 pond frogs (Pelophylax nigromaculatus) from 24 islands of the Zhoushan Archipelago and three sites on nearby mainland China and estimated the effects of the island area, population size, time since island isolation, distance to the mainland and distance to the nearest larger island on reduced genetic diversity of insular populations. The mainland populations displayed higher genetic diversity than insular populations. Genetic differentiations and no obvious gene flow were detected among the frog populations on the islands. Hierarchical partitioning analysis showed that only time since island isolation (square‐root‐transformed) and population size (log‐transformed) significantly contributed to insular genetic diversity. These results suggest that decreased genetic diversity and genetic differentiations among insular populations may have been caused by random genetic drift following isolation by rising sea levels during the Holocene. The results provide strong evidence for a relationship between retained genetic diversity and population size and time since island isolation for pond frogs on the islands, consistent with the prediction of the neutral theory for finite populations. Our study highlights the importance of the size and estimated isolation time of populations in understanding the mechanisms of genetic diversity loss and differentiation in fragmented wild populations.     

Population relationships of Simulium yahense and Simulium sanctipauli in the Firestone Rubber Plantation at Harbel, Liberia

Comparative genetic differences for the phosphoglucomutase and trehalase loci were surveyed in larval and adult blackfly populations of the onchocerciasis vectors Simulium yahense Vajime and Dunbar, and S.sanctipauli Vajime and Dunbar. Genotype frequencies for each stage and all populations were at Hardy-Weinberg equilibrium, indicating that S.yahense and S.sanctipauli remain genetically distinct. S.yahense populations from three different locations were found to be genotypically comparable. The larval population of S.yahense found in closest proximity to a S.sanctipauli population was found to express the phosphoglucomutase allele 1.33, characteristic of S.sanctipauli, with significantly greater frequency than other larval populations of S.yahense. This may constitute evidence of limited genetic introgression of S.sanctipauli with the S.yahense population.     

Phylogenetic analyses of mtDNA sequences reveal three cryptic lineages in the widespread neotropical frog Leptodactylus fuscus (Schneider, 1799) (Anura, Leptodactylidae)

Leptodactylus fuscus is a neotropical frog ranging from Panamá to Argentina, to the east of the Andes mountains, and also inhabiting Margarita, Trinidad, and the Tobago islands. We performed phylogenetic analyses of 12S rRNA, 16S rRNA, tRNA-Leu, and ND1 mitochondrial (mt) DNA sequences from specimens collected across the geographic distribution of L. fuscus to examine two alternative hypotheses: (i) L. fuscus is a single, widely distributed species, or (ii) L. fuscus is a species complex. We tested statistically for geographic association and partitioning of genetic variation among mtDNA clades. The mtDNA data supported the hypothesis of several cryptic species within L. fuscus. Unlinked mtDNA and nuclear markers supported independently the distinctness of a 'northern' phylogenetic unit. In addition, the mtDNA data divided the southern populations into two clades that showed no sister relationship to each other, consistent with high differentiation and lack of gene flow among southern populations as suggested by allozyme data. Concordance between mtDNA and allozyme patterns suggests that cryptic speciation has occurred in L. fuscus without morphological or call differentiation. This study illustrates a case in which lineage splitting during the speciation process took place without divergence in reproductive isolation mechanisms (e.g. advertisement call in frogs), contrary to expectations predicted using a biological species framework.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87 , 325–341. No claim to original US government works.     

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.     

Population genetic structure of Sorex unguiculatus and Sorex caecutiens (Soricidae, Mammalia) in Hokkaido, based on microsatellite DNA polymorphism

We investigated the genetic structure of Sorex unguiculatus and Sorex caecutiens populations in Hokkaido, Japan, using hypervariable microsatellite DNA markers. We used five microsatellite loci to type 475 S. unguiculatus individuals from 20 localities on the Hokkaido mainland and four localities from each of four offshore islands (and 11 shrews from one locality in southern Sakhalin for a particular analysis). We used six microsatellite loci to type 240 S. caecutiens individuals from 13 localities on the Hokkaido mainland. Genetic variation was high in mainland populations of both species and low in the island populations of S. unguiculatus. Allelic richness and island size were positively correlated for S. unguiculatus, suggesting that genetic drift occurred on those islands due to small population size. In addition, four insular populations of S. unguiculatus were genetically differentiated from the mainland populations, although clear phylogeographic clustering was not confirmed among populations on the Hokkaido mainland for either S. unguiculatus or S. caecutiens. Heterozygosity excess was observed in more than half of the populations including the mainland populations of the two species, suggesting recent bottleneck events in these populations. Population dynamics of the shrews might be explained by a metapopulation scheme. According to autocorrelation analysis, the extent of non-random spatial genetic structure was approximately 100 km. Isolation by distance was observed in S. unguiculatus, but not in S. caecutiens although there is a positive trend. The lack of correlation for S. caecutiens might have been due to small sample size. Thus, no obvious differences in population genetic structure were found between the two species on the Hokkaido mainland in the present study, while previous investigations using mitochondrial DNA sequences inferred that these two species might have rather different biogeographic histories.     

Novel microsatellite markers used to determine the population genetic structure of the endangered Roseate Tern, <Emphasis Type="Italic">Sterna dougallii</Emphasis>, in Northwest Atlanticand Western Australia

The Roseate Tern, Sterna dougallii, is an endangered species in the Northwest Atlantic, where it has undergone transient reductions in population size over the past 120 years. This population has been slow to regain former size and range, perhaps in part due to the female-biased sex ratio, which results in female–female pairs, reducing the average productivity of the colony. The larger populations of the Western Pacific and Indian Oceans are not endangered and there is no evidence of a biased sex ratio at breeding in Western Australia. We developed four novel microsatellite markers and adapted one other and these are the first used in the genus Sterna. We also determined the utility of these markers for 17 related species. Here we report the population genetic structure within and between two regions, the Northwest Atlantic and Western Australia. A significant finding is that the Northwestern Atlantic region has much lower allelic diversity than the Western Australia region, promoting the recommendation for increased protection of sites in this region in order to preserve remaining genetic diversity and new potential breeding habitats.     

Population genetics of threatened wild plants in Japan

Approximately one-fourth of Japan's native plant species are threatened with extinction. To conserve these species, it is critical to evaluate genetic diversity at species-level and population-level. Some factors, including population size and geographic distribution, are known to influence the population genetic diversity of wild plant species. This article briefly reviews the population genetic studies that have been conducted on wild threatened plants in Japan. A large population size or wide geographic distribution does not always lead to large genetic diversity, suggesting that historical factors such as speciation processes and population expansion often play more important roles in determining genetic diversity than the number of remnant individuals. The mating system of a species also affects genetic diversity; predominantly selfing species tend to have smaller genetic diversity than outcrossing congeners. Another issue of concern in the conservation genetics of wild plants in Japan is the genetic diversity of insular endemics, because Japan consists of many islands, and the insular flora contains many endemic and threatened species. Previous studies on endemic plants on the Bonin and the Ryukyu Islands are reviewed. Compared to the cases of the Bonin Islands or other oceanic islands, there is much larger genetic diversity in plants endemic to the Ryukyu Islands. This difference is probably the result of the differences in the geological history of these islands. Electronic Publication     

Staying close to home? Genetic differentiation of rough-toothed dolphins near oceanic islands in the central Pacific Ocean

Rough-toothed dolphins have a worldwide tropical and subtropical distribution, yet little is known about the population structure and social organization of this typically open-ocean species. Although it has been assumed that pelagic dolphins range widely due to the lack of apparent barriers and unpredictable prey distribution, recent evidence suggests rough-toothed dolphins exhibit fidelity to some oceanic islands. Using the most comprehensively extensive dataset for this species to date, we assess the isolation and interchange of rough-toothed dolphins at the regional and oceanic scale within the central Pacific Ocean. Using mtDNA and microsatellite genotyping (nDNA), we analyzed samples of insular communities from the main Hawaiian (Kaua‘i n = 93, O‘ahu n = 9, Hawai‘i n = 57), French Polynesian (n = 70) and Samoan (n = 16) archipelagos, and pelagic samples off the Northwestern Hawaiian Islands (n = 18). An overall AMOVA indicated strong genetic differentiation among islands (mtDNA F_ST = 0.265; p < 0.001; nDNA F_ST = 0.038; p < 0.001), as well as among archipelagos (mtDNA F_ST = 0.299; p < 0.001; nDNA F_ST = 0.055; p < 0.001). Shared haplotypes (n = 4) between the archipelagos may be a product of a relatively recent divergence and/or periodic exchange from poorly understood pelagic populations. Analyses using STRUCTURE and GENELAND identified four separate management units among archipelagos and within the Hawaiian Islands. These results confirm the presence of multiple insular populations within the Pacific and island-specific genetic isolation among populations attached to islands in each archipelago. Insular populations seem most prevalent where oceanographic conditions indicate high local productivity or a discontinuity with surrounding oligotrophic areas. Our findings have important implications for a little studied species that faces increasing anthropogenic threats around oceanic islands.     

The southwestern Atlantic reef fish fauna: composition and zoogeographic patterns

The Brazilian coast, the Caribbean and the tropical South Atlantic oceanic islands reef ichthyofauna separated into two major clusters: (1) the western Atlantic continental margin and Bermuda, further divided into (1a) the western North Atlantic, and (1b) the Brazilian coast; and (2) the South Atlantic oceanic islands, also divided in (2a) the Brazilian offshore islands, and (2b) Ascension and St Helena. Species geographic ranges suggest the recognition of only two western Atlantic zoogeographic provinces for tropical marine shore fishes. A Brazilian Province, including the offshore localities of Atol das Rocas, Fernando de Noronha, Trindade and St Paul's Rocks, and an expanded West Indian Province that includes Bermuda. Ascension and St Helena should be regarded as a separated Central Atlantic Province.     

Phylogeography of Xiphorhynchus fuscus (Passeriformes, Dendrocolaptidae): vicariance and recent demographic expansion in southern Atlantic forest

Knowledge of the evolutionary processes that shaped a biota is important for both academic and conservation purposes. The objective of the present study is to analyse the mitochondrial genetic variation of Xiphorhynchus fuscus (Aves: Dendrocolaptidae) from the southern Atlantic forest in Brazil and Argentina, and to discuss whether the results support different hypotheses regarding the local intraspecific diversification of this species . We sequenced 575 bp of the control region of 114 specimens collected in the Brazilian states of Bahia, Minas Gerais, Rio de Janeiro, São Paulo, Paraná, and Santa Catarina, and in the province of Misiones in Argentina. We studied the population genetic structure with analysis of molecular variance and the demographic history with multiple regression analysis, coalescence simulations, and demographic tests. Xiphorhynchus fuscus presented a significant population genetic structure (Φ_st = 0.57). Three mitochondrial lineages were described, one associated with Xiphorhynchus fuscus tenuirostris and the others with Xiphorhynchus fuscus fuscus. The data did not support the primary influence of geographical barriers or rivers in the intraspecific diversification of X. fuscus in the southern Atlantic forest. Instead, the data supported the influence of isolation by geographical distance, recent vicariance events, and demographic expansions apparently related to Pleistocene and Holocene forest dynamics.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 73–84.     

Genetic differentiation within and among island populations of the endangered plant Aster miyagii (Asteraceae), an endemic to the Ryukyu Islands

Genetic diversity was examined at 17 putative allozyme loci in 18 populations of the insular endemic plant Aster miyagii (Asteraceae). This species is geographically restricted to only three islands of the Ryukyu Islands and is on the federal list of threatened plants. Genetic differentiation within an island is small, suggesting that gene flow among populations on the same island is sufficiently large to prevent divergence. By contrast, genetic differentiation among islands is large, especially between Amamioshima Island and the other two islands, suggesting that gene flow between the islands is highly restricted. Two unique alleles are nearly fixed in populations on Amamioshima Island, which is the southernmost island of the three. Comparatively, genetic diversity is the smallest on Amamioshima Island. This genetic paucity on Amamioshima Island is probably a result of a population bottleneck at colonization or the small effective population size on this island. Genetic diversity at the species level of A. miyagii is larger than those of the species with a similar life history and of the congeneric widespread species, suggesting that the species has an old origin as an insular endemic species.     

Effects of ecogeographic variables on genetic variation in montane mammals: implications for conservation in a global warming scenario

Aim Evolutionary theory predicts that levels of genetic variation in island populations will be positively correlated with island area and negatively correlated with island isolation. These patterns have been empirically established for oceanic islands, but little is known about the determinants of variation on habitat islands. The goals of this study were twofold. Our first aim was to test whether published patterns of genetic variation in mammals occurring on montane habitat islands in the American Southwest conformed to expectations based on evolutionary theory. The second aim of this research was to develop simple heuristic models to predict changes in genetic variation that may occur in these populations as a result of reductions in available mountaintop habitat in response to global warming. Location Habitat islands of conifer forest on mountaintops in the American Southwest. Methods Relationships between island area and isolation with measures of allozyme variation in four species of small mammal, namely the least chipmunk (Tamias minimus), Colorado chipmunk (Tamias quadrivittatus), red squirrel (Tamiasciurus hudsonicus), and Mexican woodrat (Neotoma mexicana), were determined using correlation and regression techniques. Significant relationships between island area and genetic variation were used to develop three distinct statistical models with which to predict changes in genetic variation following reduction in insular habitat area arising from global warming. Results Patterns of genetic variation in each species conformed to evolutionary predictions. In general, island area was the most important determinant of heterozygosity, while island isolation was the most important determinant of polymorphism and allelic diversity. The heuristic models predicted widespread reductions in genetic variation, the extent of which depended on the population and model considered. Main conclusions The results support a generalized pattern of genetic variation for any species with an insular distribution, with reduced variation in smaller, more isolated populations. We predict widespread reductions in genetic variation in isolated populations of montane small mammals in the American Southwest as a result of global warming. We conclude that climate‐induced reductions in the various dimensions of genetic variation may increase the probability of population extinction in both the short and long term.     

Multiple SNP Markers Reveal Fine-Scale Population and Deep Phylogeographic Structure in European Anchovy (Engraulis encrasicolus L.)

Geographic surveys of allozymes, microsatellites, nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) have detected several genetic subdivisions among European anchovy populations. However, these studies have been limited in their power to detect some aspects of population structure by the use of a single or a few molecular markers, or by limited geographic sampling. We use a multi-marker approach, 47 nDNA and 15 mtDNA single nucleotide polymorphisms (SNPs), to analyze 626 European anchovies from the whole range of the species to resolve shallow and deep levels of population structure. Nuclear SNPs define 10 genetic entities within two larger genetically distinctive groups associated with oceanic variables and different life-history traits. MtDNA SNPs define two deep phylogroups that reflect ancient dispersals and colonizations. These markers define two ecological groups. One major group of Iberian-Atlantic populations is associated with upwelling areas on narrow continental shelves and includes populations spawning and overwintering in coastal areas. A second major group includes northern populations in the North East (NE) Atlantic (including the Bay of Biscay) and the Mediterranean and is associated with wide continental shelves with local larval retention currents. This group tends to spawn and overwinter in oceanic areas. These two groups encompass ten populations that differ from previously defined management stocks in the Alboran Sea, Iberian-Atlantic and Bay of Biscay regions. In addition, a new North Sea-English Channel stock is defined. SNPs indicate that some populations in the Bay of Biscay are genetically closer to North Western (NW) Mediterranean populations than to other populations in the NE Atlantic, likely due to colonizations of the Bay of Biscay and NW Mediterranean by migrants from a common ancestral population. Northern NE Atlantic populations were subsequently established by migrants from the Bay of Biscay. Populations along the Iberian-Atlantic coast appear to have been founded by secondary waves of migrants from a southern refuge.