Thesis abstract: Ecology and biogeography of island parasitoid faunas

Abstract

ISSN 1948-6596 news and update thesis abstract Ecology and biogeography of island parasitoid faunas Ana M. C. Santos 1,2,3 PhD Thesis, Silwood Park Campus, Division of Biology, Imperial College London, UK Departamento de Ecologia, Instituto de Ciencias Biologicas, Universidade Federal de Goias, 74001-970 Goiânia, GO, Brazil; 2 Centro de Biologia Ambiental, Faculdade de Ciencias da Universidade de Lisboa, C2 5th Floor, 1749-016 Lisbon, Portugal; 3 Departamento de Biodiversidad y Biologia Evolutiva, Museo Nacional de Ciencias Naturales (CSIC), C/ Jose Gutierrez Abascal 2, 28006 Madrid, Spain ana.margarida.c.santos@googlemail.com; http://www.wix.com/guidasanto1/anamcsantos Abstract. Species on islands tend to use a wider range of resources than their mainland counterparts. In this thesis I investigated whether island parasitoid communities have proportionally more idiobiont spe- cies (which tend to have a wider host range; i.e. are more generalist) than their mainland source, and which factors determine island community structure. These questions were approached using data on the distribution of Ichneumonoidea species worldwide and data from a survey conducted in the Macaronesian islands and mainland. Prior to the global analyses, I assessed whether islands and archipelagos follow the same species–area relationship, and identified which islands have comparable inventories. Globally, is- lands have proportionally more idiobionts than continental areas, and the species pool for colonization is the most important determinant of island community structure. Specimens collected in the Macaronesian region were tentatively identified using a protocol based on host dissection and DNA barcoding. At this scale, mainland faunas have proportionally more koinobiont species and island communities have a greater proportion of idiobionts. Keywords: community structure, DNA barcoding, host-parasitoid interactions, host range, island biogeo- graphy, island species–area relationship, Macaronesia, species pool Islands constitute natural laboratories for the study of evolutionary and ecological processes because of their discrete and isolated nature, small size and simplified biotas. Island faunas, es- pecially those of oceanic islands, tend to be spe- cies-poor and disharmonic, meaning that there are often fewer species on an oceanic island than on a same-sized area of mainland, and that the structure of their communities is different from their continental counterparts (e.g. some trophic guilds can be absent from island communities). The phenomenon of ecological release, typical in many island populations, occurs when a species colonizing an island encounters a new environ- ment in which competitors and/or predators are missing (Whittaker and Fernandez-Palacios 2007). One of the consequences of this process is the expansion to empty or invasible niche space, lead- ing to niche expansion and/or niche shifts, with species from island assemblages often using a wider range of resources than their counterparts from the source mainland. Therefore it is not sur- prising that many oceanic islands have a high re- presentation of generalist species when compared to the mainland (e.g. Olesen and Valido 2003). In addition, some evidence suggests that generalist species may simply have an a priori advantage during the colonization process (Piechnik et al. Parasitoids are generally defined as insects whose larvae develop to adulthood by feeding in or on the body of an arthropod host, eventually causing its death (Quicke 1997; see more details of their biology in Santos & Quicke 2011). Parasi- toids are usually divided into two different groups that reflect different life-history strategies: koino- bionts, which allow the host to continue its devel- opment after oviposition of the parasitoid, and idiobionts, which do not (Askew and Shaw 1986). Many life-history traits appear to be correlated with this dichotomy (e.g. Hawkins 1994, Quicke 1997; see Table 1). Host range, i.e. the group of frontiers of biogeography 4.1, 2012 — © 2012 the authors; journal compilation © 2012 The International Biogeography Society