Search

The distinctive morphology, color pattern, and isolated geographic locations of the various proposed taxa of the Voluta musica complex are discussed and specimens of the various taxa are illustrated. Evidence shows that populations of ancestral V. musica became genetically isolated on offshore islands during interglacial times, due to the associated higher sea levels during the Neogene, resulting in a species swarm of closely-related allopatric species. The following taxa are recognized as full species, and these include: Voluta musica, V. carneolata, V. thiarella, V. damula, and V. typica. [ABSTRACT FROM AUTHOR]

Knowledge of the mechanisms limiting connectivity and gene flow in deep-sea ecosystems is scarce, especially for deep-sea sharks. The Portuguese dogfish (Centroscymnus coelolepis) is a globally distributed and near threatened deep-sea shark. C. coelolepis population structure was studied using 11 nuclear microsatellite markers and a 497-bp fragment from the mtDNA control region. High levels of genetic homogeneity across the Atlantic (øST = -0.0091, FST = 0.0024, P > 0.05) were found suggesting one large population unit at this basin. The low levels of genetic divergence between Atlantic and Australia (øST = 0.0744, P < 0.01; FST = 0.0015, P > 0.05) further suggested that this species may be able to maintain some degree of genetic connectivity even across ocean basins. In contrast, sharks from the Mediterranean Sea exhibited marked genetic differentiation from all other localities studied (øST = 0.3808, FST = 0.1149, P < 0.001). This finding suggests that the shallow depth of the Strait of Gibraltar acts as a barrier to dispersal and that isolation and genetic drift may have had an important role shaping the Mediterranean shark population over time. Analyses of life history traits allowed the direct comparison among regions providing a complete characterization of this shark's populations. Sharks from the Mediterranean had markedly smaller adult body size and size at maturity compared to Atlantic and Pacific individuals. Together, these results suggest the existence of an isolated and unique population of C. coelolepis inhabiting the Mediterranean that most likely became separated from the Atlantic in the late Pleistocene. [ABSTRACT FROM AUTHOR]

Loss and fragmentation of habitat is a current main cause of biodiversity loss in freshwater habitats. Odonates (dragonflies and damselflies) depend on these habitats to complete their development. Fragmentation may be a particular threat for odonates because it generates a network of small habitat patches within which populations could suffer from isolation and loss of genetic diversity. The southern damselfly Coenagrion mercuriale is categorized on the IUCN red list as Near Threatened, largely because of population fragmentation and demographic declines associated with changes in land use. Small populations at the margin of this species' range are of particular concern because they would be prone to detrimental effects of habitat fragmentation if this species were a poor disperser. We sampled C. mercuriale in 16 habitat patches (localities) at 4 main sites in the department of Pasde-Calais in northwestern France to quantify factors that affect dispersal and genetic diversity. Specimens were genotyped at 12 microsatellite loci to quantify genetic diversity, genetic differentiation, and the potential effect of landscape variables on genetic differentiation, and to detect any potential source-sink structure. Habitat separation had a limiting effect on dispersal by C. mercuriale, resulting in 3 main genetic clusters and weak divergence at the main site of Vallée de la Course. Genetic differentiation was low in each main site, implying that the localities within sites were connected at scales of up to ∼2 km, albeit with some evidence for isolation at the more isolated localities. Given the degree of isolation of some areas and a lack of apparent genetic mixing in the intervening populations, any movement among the most distantly separated sites must have occurred some time ago. We identified barriers to dispersal, such as woodland, but detecting an unambiguous effect of certain variables, such as urbanization, was difficult because many landscape features were highly correlated. [ABSTRACT FROM AUTHOR]

Rapid increases in global trade and human movement have created novel mixtures of organisms bringing with them the potential to rapidly accelerate the evolution of new forms. The common brushtail possum ( Trichosurus vulpecula), introduced into New Zealand from Australia in the 19th century, is one such species having been sourced from multiple populations in its native range. Here, we combine microsatellite DNA- and GIS-based spatial data to show that T. vulpecula originating from at least two different Australian locations exhibit a population structure that is commensurate with their introduction history and which cannot be explained by landscape features alone. Most importantly, we identify a hybrid zone between the two subspecies which appears to function as a barrier to dispersal. When combined with previous genetic, morphological and captive studies, our data suggest that assortative mating between the two subspecies may operate at a behavioural or species recognition level rather than through fertilization, genetic incompatibility or developmental inhibition. Nevertheless, hybridization between the two subspecies of possum clearly occurs, creating the opportunity for novel genetic combinations that would not occur in their natural ranges and which is especially likely given that multiple contact zones occur in New Zealand. This discovery has implications for wildlife management in New Zealand because multiple contact zones are likely to influence the dispersal patterns of possums and because differential susceptibility to baiting with sodium fluoroacetate between possums of different origins may promote novel genetic forms. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The Eurasian otter (Lutra lutra) has declined significantly across its European range. In the UK, the decline was particularly severe during the late 1950’s and early 1960’s, and by the mid 1970’s the population was largely confined to strongholds in parts of Scotland, Northern Ireland, mid and West Wales and south west England. In recent years the otter population has started to recover, with otter surveys confirming an increased distribution of otters in Wales, Scotland and England. In England, population expansion and recolonisation is believed to be occurring both through breeding and by dispersal, from the west (south west England and the Welsh borders) and from the north (Scotland). However, little is known about the degree of genetic loss due to the decline, potential barriers to recolonisation, routes of dispersal, or the contribution of reintroduction programmes to population increases. This project aims to use tissues collected since 1994 (complete with geographic location) from over 500 otters found dead on roads in Wales and England, to analyse the genetic diversity and structure of otter populations. Using molecular genetic analysis of the otter population, we will identify whether and when bottlenecks occurred, whether population decline has resulted in a loss of genetic variability, and to what degree. Preliminaryanalysis from 177 otters has shown that observed is generally lower than expected het- erozygosity, and that the population is in Hardy Weinberg equilibrium for 11 out of the 15 loci. Spatial patterns in genetic data will be analysed, to identify clines, isolation by distance and genetic boundaries to gene flow, the contribution of released animals will also beassessed. Geographical information systems (GIS) will be used to map spatial genetic pat- terns and to generate hypotheses about the potential cause of genetic boundaries such as landscape or environmental features. RIASSUNTO – La genetica del paesaggio applicata allo studio di una popolazione di Lontra (Lutra lutra) in fase di espansione nel Regno Unito: risultati preliminari e metodologie potenziali. Le popolazioni di Lontra (Lutra lutra) sono significativamente diminuite in tutto il loro areale europeo. Nel Regno Unito il declino è stato particolarmente severo nell’ultima parte degli anni ’50 ed all’inizio degli anni ’60, e a metà degli anni ’70 la popolazione era sostanzialmente confinata in alcune aree della Scozia, nord Irlanda, Galles cene di Lontra ha iniziato a ri-espandersi, come indicato dai censimenti che hanno conferma- to la maggior presenza di lontre in Galles, Scozia ed Inghilterra. L’espansione e la ricolo- nizzazione in Inghilterra potrebbe essere sostenuta sia dalla riproduzione che dalla disper- sione da ovest (dall’Inghilterra del sud-ovest e dai confini col Galles), e da nord (Scozia). Tuttavia si conosce poco circa il declino di diversità genetica dovuto alla contrazione demografica, alle potenziali barriere alla ricolonizzazione, le vie di dispersione, o il con- tributo dei programmi di reintroduzione all’incremento della popolazione. Scopo di questo progetto è di usare tessuti raccolti fin dal 1994 (completi di localizzazioni geografiche) da più di 500 carcasse di lontre raccolte a seguito di incidenti stradali in Galles ed Inghilterra, per analizzare la diversità genetica e la struttura delle popolazioni. Tramite analisi genetiche molecolari, ci si propone di identificare se e quando si siano stati bottlenecks, se il declino della popolazione abbia prodotto perdite di variabilità genetica, ed in quale misura. Analisi preliminari da 177 lontre hanno mostrato che l’eterozigosi osservata è generalmente minore dell’attesa, e che la popolazione è in equilibrio di Hardy-Weinberg per 11 su 15 loci. Si anal- izzeranno i patterns spaziali dei dati genetici, al fine di identificare clini, isolamento per dis- tanza e flusso genico. Si identificherà anche l’eventuale contributo di lontre rilasciate. Sistemi informatici geografici (GIS) saranno usati per mappare i pattern geografici e per generare ipotesi sulle cause potenziali di barriere genetiche quali componenti ambientali o paesaggistiche. ntrale ed occidentale, ed Inghilterra del sud-ovest. In anni più recenti la popolazio-

Abstract: The sometimes-distant association between dispersal movements and mating strategies may govern seabird ecology. Despite their large dispersal capability, pelagic seabirds are subject to the influence of physical and non-physical barriers that may limit the magnitude of realized effective dispersal and gene flow. The Magnificent Frigatebird (Fregata magnificens) is a widespread, tropical, pelagic, sequentially monogamous seabird capable to breach physical barriers, such as land masses. Nevertheless, Mexican frigatebirds have shown movement preferences by sex (female migration and high male site fidelity), which, along with the complex female mate choice behavior, may promote breeding isolation. In order to ascertain if levels of population structure are influenced by physical or non-physical barriers, we analyzed mitochondrial DNA variation of adult Magnificent Frigatebirds breeding in the main nesting colonies in Mexico, three in the eastern Pacific Ocean and one in the Caribbean Sea. Control region sequences revealed significant genetic structure between Pacific and Caribbean frigatebirds (AMOVA, ΦSC = 0.105, P < 0.0001), but none among Pacific breeding colonies (non-significant pairwise ΦST). Whereas the C-haplotype was shared by Pacific and Caribbean frigatebirds, the T-haplotype was absent in the Caribbean. Genetic differentiation between ocean basins and available evidence of Mexican frigatebird movements suggest that in spite of the capability of frigatebirds to breach physical barriers, movement preferences by sex and mate selection acting in a large inter-oceanic scale are the prime behaviors promoting population structure, which is highly consequential for their conservation. [Copyright &y& Elsevier]

I describe the genetic structure of two frog species, Geocrinia rosea and Geocrinia lutea, using allozyme electrophoresis to understand population structure and thereby possible mechanisms of divergence and speciation. The sampling regimes represented the entire range of both species and provided replicated tests of the impact of ridges, rivers, and dry forest on gene flow. Geocrinia rosea and G. lutea were highly genetically subdivided (F ST = 0.69, 0.64, respectively). In the extreme, there were fixed allelic differences between populations that were only 4 km (G. rosea) or 1.25 km (G. lutea) apart. In addition to localized divergence, two-dimensional scaling of genetic distance allowed the recognition of broad-scale genetic groups, each consisting of several sample sites. Patterns of divergence were unrelated to the presence of ridges, rivers, or dry forest. I argue that range contraction and expansion, combined with extreme genetic divergence in single, isolated populations, best accounts for the genetic structure of these species., (© 1998 The Society for the Study of Evolution.)