ORCID Profile
0000-0002-6966-2972
Current Organisations
Mount Desert Island Biological Laboratory
,
University of Birmingham
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Publisher: The Royal Society
Date: 29-03-1996
Abstract: Despite extensive studies on the ecology and evolution of the freshwater microcrustacean Daphnia , there is little understanding of the evolutionary history of the genus. Past attempts at reconstructing phylogenetic relationships among Daphnia species have been highly controversial, mainly because of the poor taxonomy of the genus. However, following a revised taxonomy of the daphniid fauna of North America, we conducted a comprehensive appraisal of systematic relationships within the genus through the analysis of sequence ersity in 503 b.p. of the 12S rRNA gene of the mtDNA. The large sequence ergence among its 34 North American members indicates that the genus Daphnia originated during the Mesozoic, even though many lineages exhibit extreme morphological stasis. Results from both cladistic and phenetic analyses indicate the presence of three subgenera comprised of 15 species complexes. Only four of these lineages have shown active speciation over the past 3 Ma, suggesting that cladogenesis in the genus has been constrained. Our study also reveals that interspecific hybridization occurs between taxa which show very large sequence ergence (up to 14%), suggesting that reproductive isolation within the genus evolves slowly.
Publisher: Oxford University Press (OUP)
Date: 11-1998
Publisher: Wiley
Date: 23-02-2010
Publisher: Oxford University Press (OUP)
Date: 06-1999
DOI: 10.2307/2640718
Publisher: Elsevier BV
Date: 06-1996
Abstract: Although members of the crustacean genus Daphnia have been the target of much research, there is little understanding of the group's evolutionary history. We addressed this gap by inferring a phylogeny for one of the major species groups (longispina) using nucleotide sequence variation of a 525-bp segment of the mitochondrial 12S rDNA and allozyme variation at 21 loci. We identified the major lineages and their relationships, assessed the phylogenetic utility of the few morphological characters in the group, and examined Daphnia phylogeography. Nuclear and mtDNA phylogenies were generally concordant in recognizing the same four species complexes. An exception was the position of Daphnia galeata mendotae. The allozyme tree paired this species with the Daphnia rosea lineage, whereas the mtDNA trees grouped D. g. mendotae with Daphnia galeata galeata. This discordance was consistent with the reticulate evolution of nuclear genes supporting the hypothesis that D. g. mendotae represents a case of homoploid hybrid speciation. Striking morphological stasis in the longispina group was evidenced by its very limited morphological ergence over an estimated 100 MY, and by the unusual transitional saturation of the conservative 12S rRNA gene within a species group. Phylogenetic inference also provided evidence that similarities in cephalic crest shape likely resulted from convergent or parallel evolution among species. Endemism at the continental level was indicated for previously cosmopolitan species, but the estimated times of these isions were inconsistent with vicariance events suggesting recent dispersal among continents. A significant role for ergent selection in new habitats during speciation was suggested by the neighboringly sympatric distributions of four sister species pairs over broad geographic areas.
Publisher: Elsevier BV
Date: 03-2009
DOI: 10.1016/J.YMPEV.2008.11.026
Abstract: Molecular studies have enlightened our understanding of freshwater zooplankton biogeography, yet questions remain regarding the scale and commonality of geographic speciation. Here, we present a mtDNA-based phylogenetic hypothesis for 92 Daphnia species from all seven continents, with a focus on North and South America, Europe, and Australia, and use it to explore the frequency, scale, and geographical orientation of allopatric ergence events. Allopatric speciation can conservatively account for at least 42% of cladogenetic events among the species included in our study most of these involve intercontinental splits. Closely related species pairs are concentrated in the circumarctic region and between northern and southern continents, aligned with bird migration routes, suggesting recent dispersal. By contrast, deeper phylogenetic patterns are consistent with vicariance scenarios linked to continental fragmentation. The possible reasons for the puzzling persistence of these ancient patterns in light of the eroding force of dispersal are considered. Our results demonstrate the high frequency and complex pattern of allopatric speciation in this ancient, passively dispersed genus.
Publisher: Oxford University Press (OUP)
Date: 18-10-2006
Publisher: Springer Science and Business Media LLC
Date: 27-11-2014
Publisher: Springer Science and Business Media LLC
Date: 22-01-2018
DOI: 10.1038/S42003-017-0005-3
Abstract: Accurate quantification of bio ersity is fundamental to understanding ecosystem function and for environmental assessment. Molecular methods using environmental DNA (eDNA) offer a non-invasive, rapid, and cost-effective alternative to traditional bio ersity assessments, which require high levels of expertise. While eDNA analyses are increasingly being utilized, there remains considerable uncertainty regarding the dynamics of multispecies eDNA, especially in variable systems such as rivers. Here, we utilize four sets of upland stream mesocosms, across an acid–base gradient, to assess the temporal and environmental degradation of multispecies eDNA. S ling included water column and biofilm s ling over time with eDNA quantified using qPCR. Our findings show that the persistence of lotic multispecies eDNA, s led from water and biofilm, decays to non-detectable levels within 2 days and that acidic environments accelerate the degradation process. Collectively, the results provide the basis for a predictive framework for the relationship between lotic eDNA degradation dynamics in spatio-temporally dynamic river ecosystems.
Publisher: Springer Science and Business Media LLC
Date: 2009
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
No related grants have been discovered for John Colbourne.