Peter Verdyck

Rural–urban gradients and the population genetic structure of woodland ground beetles

AbstractGenetic diversity and differentiation of two carabid beetle species were examined in woodlands along rural–urban gradients in two cities (Brussels, Belgium, and Birmingham, UK), based on allozymes, studied in more than 1000 beetles. Compared to Abax ater, Pterostichus madidus showed higher levels of genetic diversity but lower genetic differentiation, probably because of its ability to survive in non-forest habitats. Higher genetic diversity in both species was observed in Brussels as compared to Birmingham. However, genetic differentiation among sites was higher in Birmingham corresponding to the more extreme degree of fragmentation and isolation between the Birmingham woodlands. The isolation-by-distance model did not explain genetic differentiation among sites within the two regions. Gene diversity in P. madidus Birmingham populations was higher in smaller urban forests with a small perimeter. A similar absence of genetic erosion in smaller and more highly modified (urban) populations was also obtained for A. ater populations from Brussels, with a higher genetic diversity in sites closer to woodland edges. This unexpected result is hypothesised to be the result of an adaptive increase of genetic diversity in more heterogeneous landscapes, closer to woodland edges and in smaller and more perturbed forests.

Low levels of genetic differentiation between Opuntia echios varieties on Santa Cruz (Galapagos)

Three processes play an important role in plant speciation: isolation, hybridization and polyploidization. Galapagos endemic Opuntia display putatively all of these processes. On this archipelago most islands are inhabited by a single Opuntia taxon. Santa Cruz, however, houses two morphologically distinct O. echios varieties (echios and gigantea). Morphological intermediates are found where these two geographically isolated varieties meet. Here we used ten microsatellite loci to reveal the population genetic structure of this system. In contrast to earlier studies, we found high genetic variability within localities. Genetic structuring was weak and no evidence for the existence of hybrids was found. The reasons for this weak genetic structure may include: the species’ hexaploid nature, high levels of gene flow, recent colonization, and the lack of geographic barriers. This first detailed genetic study on these threatened species will be important for further conservation planning.

CALLEIDA MIGRATORIA CASALE, NEW SPECIES (COLEOPTERA: CARABIDAE), A NEWLY INTRODUCED GROUND BEETLE IN THE GALAPAGOS ISLANDS, ECUADOR

Abstract This contribution reports on the discovery of Calleida migratoria Casale, new species, a ground beetle previously unknown to the Galápagos Islands. Since the recent and very strong 1997–98 El Niño event we have found this species on five of the Galápagos Islands: Isabela, Pinta, Santa Cruz, Santiago and Rabida. The species is also known from Peru and its presence in Galápagos is therefore most probably another anthropogenic introduction which has taken advantage of the unusually favourable climatic circumstances of the last El Niño. Calleida migratoria is described and a provisional identification key is added to distinguish the new taxon from its closest relatives.

The Influence of Historical Geneflow, Bathymetry and Distribution Patterns on the Population Genetics of Morphologically Diverse Galápagos’ Opuntia echios

Throughout history, remote archipelagos have repeatedly been designated natural laboratories to study evolutionary processes. The extensive, geographically structured, morphological variation within Galápagos’ Opuntia cacti has been presumed to be another example of how such processes shape diversity. However, recent genetic studies on speciation and potential effects of plasticity within this system failed to confirm earlier classification and hypothesized radiation on both global and single island levels. Detailed population genetic information, however, is crucial in conserving these semi-arid ecosystem keystone species. In this article, we re-evaluate the genetics of Opuntia echios inhabiting one of the most taxon rich places on the archipelago: Santa Cruz and its surrounding satellite islands, using microsatellite data. Our analysis revealed high genetic variability within all sampled locations, providing little support for the hypothesis of clonal reproduction. Inter-island gene flow patterns appear to be largely influenced by bathymetry and sea levels during last ice ages. Although O. echios from Seymour Norte are morphologically recognized as being a separate taxon, Daphné Major’s cacti are the most differentiated. In addition, we found a potential barrier for gene flow along the ring-like distribution of Opuntias at the western side of Santa Cruz, suggesting potential links with geology.

Morphological Variation within and between Four Closely Related Phyllotreta Species: P. dilatata, P. flexuosa, P. ochripes and P. tetrastigma (Coleoptera: Chrysomelidae)

Abstract Phyllotreta dilatata Thomson, 1866, P. flexuosa (Illiger, 1794) P. ochripes (Curtis, 1837) and P.tetrastigma (Comolli, 1837) are four closely related, morphologically similar flea beetle species which are usually distinguished according to elytral colour pattern and also show morphological differences in the genitalia. Here both uni- and multivariate analyses are used to study intra- and interspecific morphological variation for the four species. All species seem to differ in overall morphology and the results also support the idea of regarding P. tetrastigma and P. flexuosa as two different systematic entities.