Agelenids of the World

Systematics and Taxonomy of Agelenidae, a Worldwide distributed Spider Family

Contrasting patterns of hybridization in large house spiders (Tegenaria atrica group, Agelenidae)

Publication Type:Journal Article
Year of Publication:2007
Authors:P. J. P. Croucher, Jones, R. M., Searle, J. B., Oxford, G. S.
Date Published:2007
ISBN Number:0014-3820
Keywords:& Wales] [Hybridization / / Extent & nature of hybridization] [Gene, contrasting patterns of hybridization] [England / / ] [Wales / / ]., England, Eurasia, Europe, flow / Introgressive hybridization / Asymmetric introgression between, General morphology, Genetics, implications for species interactions & hybridization patterns, Land, Palaearctic region, Population genetics, species] [Zoogeography / / Distribution & species interactions, Tegenaria atrica group (Araneae)., Tegenaria atrica group [General morphology / / Multivariation analyses, United Kingdom, zones, Zoogeography

The integrity of species is not fixed and may vary geographically. Here we investigate the geographic distributions and interactions of species in the Tegenaria atrica group (Araneae: Agelenidae). Detailed mapping of T. saeva and T. gigantea in England and Wales shows them to be broadly allopatric in southern England with a tightly defined, and possibly long-standing, narrow zone of parapatry in central southern England. In the north of England (Yorkshire), by contrast, the species are broadly sympatric as a result of recent range expansions. GIS techniques are used to map the species distributions and to quantify, we believe for the first time, the intimacy of interspecific interactions. The extent and nature of hybridization in these two areas is examined through regression and multivariate analyses of morphology. We show that the relative incidence of hybridization is much greater in Yorkshire than within the parapatric zone in the south. Clear patterns of asymmetric introgression are observed in both northern and southern England, with a greater impact of T. gigantea on T. saeva than vice versa. We find no sign of morphological reproductive character displacement at the zone of parapatry that might indicate reinforcement, although we cannot exclude more subtle effects, for example via cuticular pheromones. The integrity of these two species seems to be breaking down in northern England, a process that might gain momentum as the gene pools become more similar.

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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith