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Host Groups (host + groups)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Species richness of helminth parasites in Mexican amphibians and reptiles

DIVERSITY AND DISTRIBUTIONS, Issue 4 2002
Gerardo Pérez-Ponce de León
Abstract. Amphibians and reptiles represent an important group of vertebrates in Mexico; on a global scale 10% of the biodiversity of these groups is found in the country, attaining extraordinarily high levels of endemism (60.7% and 53.7%, respectively). However, fewer than 20% of the known species of amphibians and reptiles in Mexico have been surveyed for helminths, so the inventory is far from complete. We assembled a data base that includes a total of 1246 records (entries) of which 460 correspond to helminths in amphibians and 786 to helminths in reptiles. In total, only 41 species of amphibians (14% of those occurring in Mexico) and only 118 species of reptiles (17% of those occurring in Mexico) have been studied for helminth parasites. From amphibians, 119 species of helminths belonging to 60 genera have been recorded, while 239 species of helminths representing 113 genera have been described from Mexican reptiles. One feature of the distribution of helminths of Mexican amphibians and reptiles is its asymmetry, as seen in representation of helminth groups, host groups and geographical range. However, such statistical asymmetry might be an artefact of sampling effort. Based on our data, we estimate that if all the herpetofauna of Mexico could be studied in the following years, approximately 827 additional species of helminths from amphibians and approximately 1403 from reptiles would be described. [source]

Spanning the gap: experimental determination of paratenic host specificity of horsehair worms (Nematomorpha: Gordiida)

INVERTEBRATE BIOLOGY, Issue 1 2003
Ben Hanelt
Abstract. Details of the life cycle of freshwater nematomorphs (gordiids) remain unclear. Free-living aquatic larval gordiids must make a critical transition from an epibenthic aquatic environment to terrestrial hosts. In order to identify potential hosts capable of bridging this ecological gap, the specificity of paratenic hosts of three common species of North American gordiids was investigated. All three species were characterized by an identical infection pattern: low host specificity. Gordiids were able to encyst within annelids, mollusks, crustaceans, insects and a vertebrate. Three species of putative host (a turbellarian, a water mite, and a mosquito larva) were not infected with any of the gordiid species. Internal defense reactions (IDR) and feeding behaviors are implicated as preventing infection in these species. Several of the other host species produced either an IDR or an immune reaction to the cysts, although reactions to the cysts were highly variable between species. In most species, IDR did not cause noticeable harm to the encysted larvae. It is proposed that although many species are easily infected with gordiid cysts, most do not act as natural paratenic hosts. For some of these host groups, especially snails, a role as reservoir host is suggested. Of all hosts included in this study, aquatic insects were identified as the hosts likely responsible for spanning the ecological gap and acting as true hosts for gordiids. [source]

Property rights for social inclusion: Migrant strategies for securing land and livelihoods in Papua New Guinea

ASIA PACIFIC VIEWPOINT, Issue 1 2009
Gina Koczberski
Abstract This paper examines the broad range of informal land transactions and arrangements migrants are entering into with customary landowners to gain access to customary land for export cash cropping in the oil palm belt of West New Britain, Papua New Guinea. Whilst these arrangements can provide migrants with relatively secure access to land, there are instances of migrants losing their land rights. Typically, the land tenure arrangements of migrants with more secure access to land are within a framework of property rights for social inclusion whereby customary landowners' inalienable rights to land are preserved and the ,outsider' becomes an ,insider' with ongoing use rights to the land. Through socially embedding land transactions in place-based practices of non-market exchange, identities of difference are eroded as migrants assume identities as part of their host groups. This adaptability of customary land tenure and its capacity to accommodate large migration in-flows and expanding commodity production undermines the argument common amongst proponents of land reform that customary tenure is static and inflexible. Before such claims are heeded, there must be more detailed empirical investigations of the diverse range of land tenure regimes operating in areas of the country experiencing high rates of immigration. [source]

Divergent host plant adaptation drives the evolution of sexual isolation in the grasshopper Hesperotettix viridis (Orthoptera: Acrididae) in the absence of reinforcement

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2010
TONY GRACE
Early stages of lineage divergence in insect herbivores are often related to shifts in host plant use and divergence in mating capabilities, which may lead to sexual isolation of populations of herbivorous insects. We examined host preferences, degree of differentiation in mate choice, and divergence in cuticular morphology using near-infrared spectroscopy in the grasshopper Hesperotettix viridis aiming to understand lineage divergence. In Kansas (USA), H. viridis is an oligophagous species feeding on Gutierrezia and Solidago host species. To identify incipient mechanisms of lineage divergence and isolation, we compared host choice, mate choice, and phenotypic divergence among natural grasshopper populations in zones of contact with populations encountering only one of the host species. A significant host-based preference from the two host groups was detected in host-paired feeding preference studies. No-choice mate selection experiments revealed a preference for individuals collected from the same host species independent of geographic location, and little mating was observed between individuals collected from different host species. Female mate choice tests between males from the two host species resulted in 100% fidelity with respect to host use. Significant differentiation in colour and cuticular composition of individuals from different host plants was observed, which correlated positively with host choice and mate choice. No evidence for reinforcement in the zone of contact was detected, suggesting that divergent selection for host plant use promotes sexual isolation in this species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 866,878. [source]