Process‐based and correlative modeling of desert mistletoe distribution: a multiscalar approach

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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.

Section: Discussionmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 97%

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

Lira‐Noriega

Peterson

2014

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“…Current theory (Sober on, 2007(Sober on, , 2010Peterson et al, 2011) considers that the unlinked variables needed for niche/distributional models are abiotic (or reflective of habitat/vegetation structure), but this exclusion of biotic interactors may not be justified (Anderson, 2013;Lira-Noriega et al, 2013). Seemingly, the only restriction prohibiting the use of a biotic interactor as a variable in building a niche/distribution model would be if its values are affected by (linked to) the population level of the focal species ( Fig.…”

Section: Niche Perspectives and Predictor Variablesmentioning

confidence: 99%

“…These depictions of the range of the interactor likely would be maps of binary presence/absence or continuous representations of suitability (or probability of presence) within the areas occupied. Indeed, many recent studies have used biotic interactors as predictors (Meier et al, 2010;Jaeschke et al, 2012;Giannini et al, 2013), although seldom considering whether or not they constitute unlinked variables (Lira-Noriega et al, 2013).…”

Section: Niche Perspectives and Predictor Variablesmentioning

confidence: 99%

When and how should biotic interactions be considered in models of species niches and distributions?

Anderson

2016

152

134

Biotic interactions can influence the ranges and abundances of species, but no clear guidelines exist for integrating them into correlative models of niches and distributions. Niche/distributional models characterize environmental/habitat suitability or species presence using predictor variables unaffected by (= unlinked to) the population of the focal species. Such variables (termed ‘scenopoetic’) typically have been considered to include only abiotic factors. In contrast, population–demographic approaches model the abundance of the focal species by including linked predictor variables, which frequently are biotic interactors. Nevertheless, a focal species might hold no, or negligible, population‐level effects on its biotic interactors. Hence, contrary to current theory, such interactors would represent unlinked variables valid and potentially very useful for niche/distributional models. Consideration of population‐level effects indicates that facilitators and affecting amensals (species that negatively affect another species but are not affected by it) constitute unlinked variables, but commensals and affected amensals do not. For competitors, mutualists, predators/prey, consumers/resources, and parasites/hosts, additional information is necessary. Specifically, available ecological/natural history information for the particular species involved (e.g. regarding specificity) and theory regarding ecological networks can allow identification of interactors that are likely to be unlinked or nearly so. Including an unlinked biotic interactor as a predictor variable in a niche/distributional model should improve predictions when the effects of the biotic interactor vary across the study region, or in another place or time period. Other relevant interactors must be taken into account by post‐processing a niche/distributional model, or via population–demographic models that require abundance data over time. This framework should improve current correlative models and highlights areas requiring progress.

“…Macroecological analyses are powerful in that they allow patterns to be drawn over large taxonomic and geographic extents, but also have some limitations. First, they frequently have a coarse resolution (Beck et al, 2012;Lira-Noriega, Sobéron, & Miller, 2013), but species often interact with their environment at finer (microhabitat) scale. Microhabitat conditions are not always captured by macroecological variables, and can provide a more accurate description of the effect of environmental variation on individuals (De Frenne et al, 2019;Ficetola et al, 2018;Moore, Stow, & Kearney, 2018;Scheffers, Edwards, Diesmos, Williams, & Evans, 2014).…”

Section: Introductionmentioning

confidence: 99%

Transgressive niche across a salamander hybrid zone revealed by microhabitat analyses

Ficetola

Lunghi

Cimmaruta

et al. 2019

Aim Hybrid populations can have intermediate, conserved or transgressive niches, compared to the parental species. Fine‐scale analyses can improve our understanding of niche evolution, but information on microhabitat differences between parental species and hybrids is extremely scarce for animal populations. We assessed the pattern and role of niche variation along a hybrid zone, by investigating differences in microhabitat selection between terrestrial cave salamander species (Hydromantes ambrosii and Hydromantes italicus) and their hybrids. We tested whether introgressed populations show intermediate, conserved or transgressive niche, compared to parental species. Furthermore, we compared body condition index (BCI) among individuals observed in different microhabitats (different areas of caves), to assess the potential advantages of exploiting specific microhabitats. Location We surveyed ~700 cave sectors in Italy, across the whole range of the two parental species and along their contact zone. Methods We recorded salamander distribution and measured microhabitat features influencing salamander distribution: humidity, temperature and incident light. We tested niche differences between parental species and hybrids, and analysed spatial variation of body condition. Results We detected significant niche shifts between parental species and hybrids. Introgressed populations showed a transgressive niche and exploited sectors with warmer temperature, lower humidity and more light, compared to the non‐introgressed ones. Introgressed salamanders were better able to exploit the microhabitat conditions that are frequently found nearby cave entrance. For males, BCI was significantly higher in individuals found close to the cave entrance. Main conclusions The transgressive niche of hybrids between H. ambrosii and H. italicus indicates niche expansion towards harsh environmental conditions, and such transgressive segregation allows exploiting environments with higher food availability. The ability to exploit dry and warm sectors can provide important advantages to hybrid populations that can better persist under stressful conditions. Transgressive niche can be important for long‐term persistence and evolution within hybrid zones.