Population structure of a vector‐borne plant parasite

Abstract

Parasites are among the most diverse groups of life on Earth, yet complex natural histories often preclude studies of their speciation processes. The biology of parasitic plants facilitates in situ collection of data on both genetic structure and the mechanisms responsible for that structure. Here, we studied the role of mating, dispersal and establishment in host race formation of a parasitic plant. We investigated the population genetics of a vector-borne desert mistletoe (Phoradendron californicum) across two legume host tree species (Senegalia greggii and Prosopis velutina) in the Sonoran desert using microsatellites. Consistent with host race formation, we found strong host-associated genetic structure in sympatry, little genetic variation due to geographic site and weak isolation by distance. We hypothesize that genetic differentiation results from differences in the timing of mistletoe flowering by host species, as we found initial flowering date of individual mistletoes correlated with genetic ancestry. Hybrids with intermediate ancestry were detected genetically. Individuals likely resulting from recent, successful establishment events following dispersal between the host species were detected at frequencies similar to hybrids between host races. Therefore, barriers to gene flow between the host races may have been stronger at mating than at dispersal. We also found higher inbreeding and within-host individual relatedness values for mistletoes on the more rare and isolated host species (S. greggii). Our study spanned spatial scales to address how interactions with both vectors and hosts influence parasitic plant structure with implications for parasite virulence evolution and speciation.

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

“…For example, P. calyculatus in Oaxaca preferentially infects Anacardiaceae despite the abundance of Fabaceae in the region, which, instead, are preferentially infected by sympatric P. auriculatus (D ıaz Infante et al, 2016). Also, host specificity may be scale dependent, which can explain the apparently contradictory results on the importance of host preferences to genetic differentiation in Phoradendron californicum at different spatial scales (Lira-Noriega et al, 2015;Yule et al, 2016). In the present case, scale-dependent host preferences would explain why Liquidambar (Altingiaceae) appears to be the main host for P. schiedeanus in central Veracruz (L opez de Buen & Ornelas, 2002;Kuijt, 2009;Cocoletzi et al, 2016), but is less frequently (or not) infected throughout the rest of its distribution range (Fig.…”

Efficiency of an air curtain as an anti‐insect barrier: the honey bee as a model insect

“…The number of insect species has been estimated at five million . Their dispersal ability presents a concern because they can transmit organisms and viruses that are pathogenic to humans, other animals (including pets, livestock and poultry) and plants . They can also induce food‐borne diseases by contaminating foodstuffs .…”

“…8,9 Their dispersal ability presents a concern because they can transmit organisms and viruses that are pathogenic to humans, [10][11][12][13][14] other animals (including pets, livestock and poultry) [15][16][17][18] and plants. 19,20 They can also induce food-borne diseases by contaminating foodstuffs. 15 Among insects, flying species represent the predominant vectors of diseases.…”

Reproductive ecology of a parasitic plant differs by host species: vector interactions and the maintenance of host races

“…However, many parasitic species likely contain vast cryptic diversity. Indeed, recent population genetic studies have uncovered evidence of host-associated genetic differentiation at small geographic scales in both holoparasitic (De Vega et al 2008;Thurgood et al 2008) and hemiparasitic (Jerome and Ford 2002;Zuber and Widmer 2009;Yule et al 2016) plant species. The mechanisms responsible for generating this differentiation in parasitic plants are not well understood relative to those in other parasitic taxa.…”

“…Second, we ask whether desert mistletoe's interactions with pollinators differ according to host species. For mistletoes of two host species known to form distinct host races (Yule et al 2016), we characterize pollen and Yule and Bronstein 6 nectar production, as well as the pollinator community composition and degree to which 92 pollinators specialize on a given host race. We use our phenological and pollinator data to 93 estimate the strength of these pre-zygotic isolating barriers between the host races.…”