Biomedical subjects

Trevor J C Beebee

Publications and source records attributed to Trevor J C Beebee.

5 recordsLinked to original sources

PubMed2005

Lusitania revisited: a phylogeographic analysis of the natterjack toad Bufo calamita across its entire biogeographical range.

Attempts to understand the current distributions of plants and animals require both historical and ecological information. Phylogeography has proved highly effective in elucidating historical events such as postglacial colonisations in north temperate zones. However, interesting questions still await resolution. Lusitanian distributions of fauna and flora in western Europe, for example, have puzzled biogeographers for more than 150 years. Lusitanian species have highly disjunct distributions in Ireland and in Iberia, often with few or no other populations inbetween. Despite much debate, no agreed explanation for Lusitanian distributions has yet emerged. We investigated the phylogeographic structure of one Lusitanian species, the natterjack toad Bufo calamita, using mitochondrial DNA control region sequences and allelic variation at eight microsatellite loci. Our results show that this amphibian must have survived in north European refugia, as well as in Iberia, during and since the last (Weichselian) glacial maximum around 20,000 years before present (BP). Subsequent local recolonisation after the Younger Dryas cooling around 11,000 years BP best explains the Lusitanian aspect of natterjack toad distribution.

Animals↗

PubMed2003

Population genetics of a successful invader: the marsh frog Rana ridibunda in Britain.

We investigated the genetic outcome of successful invasion by an alien species, the marsh frog Rana ridibunda, in Britain. Twelve adults translocated from Hungary into Kent (Romney) in 1935 resulted rapidly in a large localized population. A further successful translocation in 1973 from Romney to Sussex (Lewes), together with other range extensions, provided an opportunity to test bottleneck effects during colonization events. Romney and Lewes frogs had similar genetic diversities to those in Hungary at 14 random amplified polymorphic DNA marker (RAPD) and five microsatellite loci. The introduced populations were, however, differentiated genetically from each other and from a reference population in Hungary. Fitness assessments (larval growth and survival) revealed no differences between the Lewes and Romney populations. Despite starting with few founders, significant bottleneck effects on R. ridibunda in Britain were therefore undetectable, presumably because population expansions were rapid immediately after the translocations.

Alleles↗

PubMed2003

Population on the verge of a mutational meltdown? Fitness costs of genetic load for an amphibian in the wild.

The fitness costs of high genetic load in wild populations have rarely been assessed under natural conditions. Such costs are expected to be greatest in small, bottlenecked populations, including those occurring near range edges. Britain is at the northwesterly range limit of the natterjack toad Bufo calamita. We compared fitness attributes in two populations of this amphibian with very different recent histories. Key larval fitness attributes in B. calamita, notably growth rate and metamorph production, were substantially higher in the large outbreeding population (Ainsdale) than in the small and isolated one (Saltfleetby). These differences were manifest under seminatural conditions, when larvae were reared in mesh cages within breeding ponds at the site of the small population, and were exacerbated by high stress treatments. The results indicate that genetic load effects can be sufficiently severe enough to predispose extinction over relatively short time frames, as predicted by extinction vortex models.

Animals↗

PubMed2002

Ecological responses to recent climate change.

There is now ample evidence of the ecological impacts of recent climate change, from polar terrestrial to tropical marine environments. The responses of both flora and fauna span an array of ecosystems and organizational hierarchies, from the species to the community levels. Despite continued uncertainty as to community and ecosystem trajectories under global change, our review exposes a coherent pattern of ecological change across systems. Although we are only at an early stage in the projected trends of global warming, ecological responses to recent climate change are already clearly visible.

Animals↗

PubMed1999

Prototheca richardsi, a pathogen of anuran larvae, is related to a clade of protistan parasites near the animal-fungal divergence.

Prototheca richardsi is a protist of uncertain taxonomy which mediates growth inhibition in anuran larvae. Cells of P. richardsi were isolated from tadpole faeces and DNA was purified by Qiagen chromatography. Nuclear small-subunit (18S) rDNA (ssu-rDNA) was amplified by PCR using universal primers, cloned, and six clones (two from each of three separate isolates) were sequenced. All clones yielded an essentially identical sequence of 1802 nucleotides. In situ hybridization of fluorescent Prototheca-specific oligonucleotide probes, designed using the derived 18S rDNA sequence, confirmed that the sequence was indeed from P. richardsi cells and not from other components of tadpole faeces. The P. richardsi sequence was aligned with ssu-rDNA from a range of other eukaryotes, and phylogenetic analyses were carried out using several inference methods. P. richardsi consistently and stably grouped within a novel clade that contains rDNAs from an apparently heterodisperse group of parasitic micro-organisms assigned to the class Ichthyosporea. P. richardsi is evidently misplaced in the genus Prototheca, and the authors propose its inclusion in a new genus Anurofeca.

Animals↗