Range‐wide ecological niche comparisons of parasite, hosts and dispersers in a vector‐borne plant parasite system

Abstract

Aim To test whether the distribution of the mistletoe Phoradendron californicum is mediated by host distributions (host niche hypothesis, HNH), or by factors such as the mistletoe's autecology (parasite niche hypothesis, PNH) or that of its vectors (vector niche hypothesis, VNH). Our null hypothesis is that the ecological niche of the mistletoe will not be distinct from that of its hosts or vectors; alternatively, mistletoe infections might appear in hosts only in regions where host distributions overlap suitable conditions for the parasite. Location Sonoran and Mojave deserts, western North America. Methods We used ecological niche modelling approaches to summarize suitable environmental conditions for hosts infected and uninfected with mistletoes, as well as for avian dispersers during winter and throughout the year. We compared ecological niches among pairs of species using background similarity tests in relation to the climatic conditions available and accessible to each species. Results Niche comparisons supported all PNH expectations, but none of the predictions of HNH or VNH. Main conclusions Hosts and dispersers of mistletoes generally have distinct ecological niches; mistletoe infections occur in non‐random environmental subsets of host and disperser ecological niches; mistletoe infections in different hosts, however, occur under similar climatic conditions. Hence, in this system, the parasite has a rather strictly circumscribed ecological niche, and host species become infected with mistletoe only where they overlap its suitable areas.

The influence of climatic niche preferences on the population genetic structure of a mistletoe species complex

“…The life cycle of parasitic angiosperms often involves interactions with multiple species. Therefore, these parasites represent ideal systems to test evolutionary hypotheses regarding host specificity, transmission and diversification (Kuijt, 1969(Kuijt, , 2009Esp ındola et al, 2014;Lira-Noriega & Peterson, 2014). Recent work, mainly in animals, has shown that parasitism is a major driver of species diversification (Wiens et al, 2015), and host switching has been considered to be the most common form of parasitic population divergence and speciation (de Vienne et al, 2013;Hoberg & Brooks, 2015).…”

Host specificity in parasitic plants—perspectives from mistletoes

“…The works of Lira-Noriega et al (2015) and Lira-Noriega and Peterson (2014) on the mistletoe Phoradendron californicum have demonstrated that the distribution of this species is strongly affected by the evolutionary hot spots where the host, dispersal vectors and environmental condition of the mistletoes overlap. Their studies highlight the importance of the geological past interacting with the mistletoe–host associations in structuring phylogeography and initiating host races in mistletoes.…”

“…Their studies highlight the importance of the geological past interacting with the mistletoe–host associations in structuring phylogeography and initiating host races in mistletoes. Using herbarium voucher specimens, Lira-Noriega and Peterson (2014) tested three niche hypotheses (host, vector and parasite) that likely mediate mistletoe distribution and found that host availability alone does not determine mistletoe establishment. Instead, suitable environmental conditions for the mistletoe are a prerequisite.…”

“…Mistletoes that are initially capable of utilizing several host species may also become restricted to a subset of available hosts within an area (Barlow and Wiens 1977; Amico et al 2007; Okubamichael et al 2011 a ; Kavanagh and Burns 2012, Lira-Noriega et al 2015; Lira-Noriega and Peterson 2014). Generalist mistletoe species are therefore often composed of distinct host-specific populations (e.g.…”

“…Generalist mistletoe species are therefore often composed of distinct host-specific populations (e.g. Lira-Noriega et al 2015; Lira-Noriega and Peterson 2014). These host-specific populations of mistletoes could eventually speciate to produce host races (Norton and de Lange 1999; Jerome and Ford 2002; Lira-Noriega et al 2015).…”