RESEARCH PAPER Pollinators, flowering phenology and floral longevity in two Mediterranean Aristolochia species, with a review of flower visitor records for the genus R. Berjano, P. L. Ortiz, M. Arista & S. Talavera Departamento de Biologı´a Vegetal y Ecologı´a, Facultad de Biologı´a, Universidad de Sevilla, Sevilla, Spain INTRODUCTION Plants with specialised floral morphologies (i.e. phenotyp- ically specialised flowers) often also possess functionally specialised pollination systems (e.g. plant adapted to bird pollination or fly pollination; Ollerton et al. 2007a). In some of these specialised pollination systems, no floral reward is offered and pollinators are attracted by decep- tion (Dafni 1984). This is the case for Aristolochia flowers, which are sapromyiophilous or micromyiophilous (fungus gnat flowers) flowers that attract their pollinators by imi- tating brood sites (Proctor et al. 1996), though in some cases, the larvae of pollinators feed on decaying flowers (Hime & Costa 1985; Sakai 2002). The pollination biology of Aristolochia species has been studied for more than two centuries (e.g. Sprengel 1793; Carr 1924; Sakai 2002; Burgess et al. 2004). A wide vari- ety of visitors have been found inside Aristolochia flowers, including different groups of arthropods (Petch 1924; Burgess et al. 2004; Valdivia and Niemeyer 2007), but dipterans are the most common. The number of dipteran families that visit the different Aristolochia species is quite variable, but only some groups carry pollen loads and function as pollinators (Table 1). However, the level of ecological specialisation (Ollerton et al. 2007a) of most Aristolochia species remains unclear. Some studies (e.g. those on A. littoralis, A. maxima, A. inflata or A. pallida) have revealed that only one or a few dipteran species are pollinators, which points to a high level of ecological spe- cialisation (Hall & Brown 1993; Sakai 2002; Rulik et al. 2008). Nevertheless, when a single species is extensively studied, a higher level of generalisation can be uncovered (e.g. A. grandiflora; Hart 1897; Cammerloher 1923; Petch 1924; Hilje 1984; Burgess et al. 2004). Most knowledge about pollination systems in Aristolo- chia comes from tropical species with extended flowering periods and short-lived flowers (e.g. Hilje 1984; Hall & Brown 1993; Sakai 2002). Little is known, however, about the pollination of Mediterranean Aristolochia species (Rulik et al. 2008). In Mediterranean ecosystems, environ- mental conditions are unpredictable (Cowling et al. 1996; Rodo ´ & Comı´n 2001) and pollinator availability Keywords Aristolochia baetica; Aristolochia paucinervis; Aristolochiaceae; floral phenology; Mediterranean; pollinator; Spain. Correspondence R. Berjano, Departamento de Biologı´a Vegetal y Ecologı´a, Universidad de Sevilla, Apdo. 1095, 41080 Sevilla, Spain. E-mail: regina@us.es Editor J. Arroyo Received: 18 December 2007; Accepted: 23 June 2008 doi:10.1111/j.1438-8677.2008.00131.x ABSTRACT The pollination of Aristolochia involves the temporary confinement of visi- tors inside the flower. A literature review has shown that some species are visited by one or a few dipteran families, while others are visited by a wider variety of dipterans, but only some of these are effective pollinators. We observed flowering phenology and temporal patterns of pollinator atten- dance in diverse populations of Aristolochia baetica and A. paucinervis, two species that grow in SW Spain, frequently in mixed populations. The two species had overlapping floral phenologies, extended flowering periods and long-lived flowers. A. baetica attracted a higher number of visitors than A. paucinervis. Drosophilids and, to a lesser extent, phorids, were the main pollinators of A. baetica, whereas in A. paucinervis, phorids were the only pollinators. Attendance to A. paucinervis flowers by phorids in mixed popu- lations was markedly lower than in pure populations. This effect was more evident in years with lower pollinator density. Our results suggest that A. baetica and A. paucinervis may compete for pollinators in mixed popula- tions. Plant Biology ISSN 1435-8603 6 Plant Biology 11 (2009) 6–16 ª 2008 German Botanical Society and The Royal Botanical Society of the Netherlands