Behavioral, Molecular, and Morphological Evidence for a Hybrid Zone between Chrysochus auratus and C. cobaltinus (Coleoptera: Chrysomelidae)

In this article, we describe a hybrid zone between the chrysomelid beetles, Chrysochus auratus (F.), andC. cobaltinus LeConte, which have historically been considered as having allopatric distributions. By combining field studies with surveys of museum specimens, we documented that in western North America there are two regions in which these beetles are sympatric, and four additional regions in which populations of the two species are Washington, we found an ≈25 km wide area of sympatry in which the two species freely interbreed. Morphological and allozyme differences between the species allowed us to demonstrate that individuals with intermediate coloration in this area are indeed hybrids; all 22 putative hybrids we assayed for allozyme variation were heterozygous at each of three species-specific loci. Museum specimens revealed that the two species have been hybridizing in this region at least since 1952. Within the hybrid zone, ≈10-15% of the beetles is apparently F1 hybrids. At one focal site, 22.9% of all matings involved heterospecific pairs and 20.8% of all matings involved at least one hybrid individual. Although we found no molecular evidence of introgression between the two species, morphometric results and preliminary ecological data suggest possible past introgression or weak ongoing introgression. We discuss the implications of our findings for the specific status of these two species. This system appears well suited to provide answers to long-standing questions concerning the evolution of premating barriers between hybridizing species. In addition, hybridization between these two beetle species with differing host ranges will allow us to test the hypothesis that ecologically significant traits such as diet breadth can be gained via introgression

Constraints on the evolution of toxin-resistant Na,K-ATPases have limited dependence on sequence divergence

A growing body of theoretical and experimental evidence suggests that intramolecular epistasis is a major determinant of rates and patterns of protein evolution and imposes a substantial constraint on the evolution of novel protein functions. Here, we examine the role of intramolecular epistasis in the recurrent evolution of resistance to cardiotonic steroids (CTS) across tetrapods, which occurs via specific amino acid substitutions to the α-subunit family of Na,K-ATPases (ATP1A). After identifying a series of recurrent substitutions at two key sites of ATP1A that are predicted to confer CTS resistance in diverse tetrapods, we then performed protein engineering experiments to test the functional consequences of introducing these substitutions onto divergent species backgrounds. In line with previous results, we find that substitutions at these sites can have substantial background-dependent effects on CTS resistance. Globally, however, these substitutions also have pleiotropic effects that are consistent with additive rather than background-dependent effects. Moreover, the magnitude of a substitution’s effect on activity does not depend on the overall extent of ATP1A sequence divergence between species. Our results suggest that epistatic constraints on the evolution of CTS-resistant forms of Na,K-ATPase likely depend on a small number of sites, with little dependence on overall levels of protein divergence. We propose that dependence on a limited number sites may account for the observation of convergent CTS resistance substitutions observed among taxa with highly divergent Na,K-ATPases (See S1 Text for Spanish translation)

recommendations from the CVBD World Forum

The human-animal bond has been a fundamental feature of mankind's history for millennia. The first, and strongest of these, man's relationship with the dog, is believed to pre-date even agriculture, going back as far as 30,000 years. It remains at least as powerful today. Fed by the changing nature of the interactions between people and their dogs worldwide and the increasing tendency towards close domesticity, the health of dogs has never played a more important role in family life. Thanks to developments in scientific understanding and diagnostic techniques, as well as changing priorities of pet owners, veterinarians are now able, and indeed expected, to play a fundamental role in the prevention and treatment of canine disease, including canine vector-borne diseases (CVBDs).The CVBDs represent a varied and complex group of diseases, including anaplasmosis, babesiosis, bartonellosis, borreliosis, dirofilariosis, ehrlichiosis, leishmaniosis, rickettsiosis and thelaziosis, with new syndromes being uncovered every year. Many of these diseases can cause serious, even life-threatening clinical conditions in dogs, with a number having zoonotic potential, affecting the human population.Today, CVBDs pose a growing global threat as they continue their spread far from their traditional geographical and temporal restraints as a result of changes in both climatic conditions and pet dog travel patterns, exposing new populations to previously unknown infectious agents and posing unprecedented challenges to veterinarians.In response to this growing threat, the CVBD World Forum, a multidisciplinary group of experts in CVBDs from around the world which meets on an annual basis, gathered in Nice (France) in 2011 to share the latest research on CVBDs and discuss the best approaches to managing these diseases around the world.As a result of these discussions, we, the members of the CVBD Forum have developed the following recommendations to veterinarians for the management of CVBDs

Vector-Borne Diseases - constant challenge for practicing veterinarians: recommendations from the CVBD World Forum

The human-animal bond has been a fundamental feature of mankind's history for millennia. The first, and strongest of these, man's relationship with the dog, is believed to pre-date even agriculture, going back as far as 30,000 years. It remains at least as powerful today. Fed by the changing nature of the interactions between people and their dogs worldwide and the increasing tendency towards close domesticity, the health of dogs has never played a more important role in family life. Thanks to developments in scientific understanding and diagnostic techniques, as well as changing priorities of pet owners, veterinarians are now able, and indeed expected, to play a fundamental role in the prevention and treatment of canine disease, including canine vector-borne diseases (CVBDs)

Low rates of iridoid glycoside hydrolysis in two Longitarsus leaf beetles with different feeding specialization confer tolerance to iridoid glycoside containing host plants

Pankoke H, Dobler S. Low rates of iridoid glycoside hydrolysis in two Longitarsus leaf beetles with different feeding specialization confer tolerance to iridoid glycoside containing host plants. Physiological Entomology. 2015;40(1):18-29.Iridoid glycosides are plant defence compounds that are deterrent and/or toxic for unadapted herbivores but are readily sequestered by dietary specialists of different insect orders. Hydrolysis of iridoid glycosides by -glucosidase leads to protein denaturation. Insect digestive -glucosidases thus have the potential to mediate plant-insect interactions. In the present study, mechanisms associated with iridoid glycoside tolerance are investigated in two closely-related leaf beetle species (Coleoptera: Chrysomelidae) that feed on iridoid glycoside containing host plants. The polyphagous Longitarsus luridusScopoli does not sequester iridoid glycosides, whereas the specialist Longitarsus tabidusFabricius sequesters these compounds from its host plants. To study whether the biochemical properties of their -glucosidases correspond to the differences in feeding specialization, the number of -glucosidase isoforms and their kinetic properties are compared between the two beetle species. To examine the impact of iridoid glycosides on the -glucosidase activity of the generalist, L. luridus beetles are kept on host plants with or without iridoid glycosides. Furthermore, -glucosidase activities of both species are examined using an artificial -glucosidase substrate and the iridoid glycoside aucubin present in their host plants. Both species have one or two -glucosidases with different substrate affinities. Interestingly, host plant use does not influence the specific -glucosidase activities of the generalist. Both species hydrolyse aucubin with a much lower affinity than the standard substrate. The neutral pH reduces the -glucosidase activity of the specialist beetles by approximately 60% relative to its pH optimum. These low rates of aucubin hydrolysis suggest that the ability to sequester iridoid glycosides has evolved as a key to potentially preventing iridoid glycoside hydrolysis by plant-derived -glucosidases