Revisiting the role of dissimilarity of host communities in driving dissimilarity of ectoparasite assemblages: non-linearvslinear approach

Abstract

We revisited the role of dissimilarity of host assemblages in shaping dissimilarity of flea assemblages using a non-linear approach. Generalized dissimilarity models (GDMs) were applied using data from regional surveys of fleas parasitic on small mammals in four biogeographical realms. We compared (1) model fit, (2) the relative effects of host compositional and phylogenetic turnover and geographic distance on flea compositional and phylogenetic turnover, and (3) the rate of flea turnover along gradients of host turnover and geographic distance with those from earlier application of a linear approach. GDMs outperformed linear models in explaining variation in flea species turnover and host dissimilarity was the best predictor of flea dissimilarity, irrespective of scale. The shape of the relationships between flea compositional turnovers along host compositional turnover was similar in all realms, whereas turnover along geographic distance differed among realms. In contrast, the rate of flea phylogenetic turnover along gradients of host phylogenetic turnover differed among realms, whereas flea phylogenetic turnover did not depend on geographic distance in any realm. We demonstrated that a non-linear approach (a) explained spatial variation in parasite community composition better than and (b) revealed patterns that were obscured by earlier linear analyses.

Contrasting drivers of diversity in hosts and parasites across the tropical Andes

“…We downloaded rasters of each of the bioclim variables using the "raster" package in R (version 3.5.1) at 2.5-arc minute resolution and cropped them to our study area (Peru). Then, we ran principle components analyses on the temperature variables (bioclim variables 1 to 11) and precipitation variables (12)(13)(14)(15)(16)(17)(18)(19) to create composite measures of temperature and precipitation across Peru. PC1 of the temperature variables (hereafter "temperature") explained 82% of variation in those variables.…”

“…geographic distance (4,10,18). This modeling framework is better suited than linear matrix regression to identifying key factors underlying turnover in complex environments (19)(20)(21).…”

Host phylogenetic diversity predicts the global extent and composition of tree pests

“…We used generalised dissimilarity models (GDM) to assess the relationship between pest compositions and the phylogenetic composition of hosts, climate, geographic distances, and country per capita gross domestic product (GDP). GDMs are a type of matrix regression (Ferrier et al, 2007) that can account for the non‐linear change of pest compositions along with explanatory variables and have been shown to provide a better fit to parasite compositional change than linear approaches (Mescht et al, 2017). Differences in pest assemblages were quantified using the Jaccard index.…”

Host specificity of flea parasites of mammals from the Andean Biogeographic Region

“…Stephanocircidae and Ctenophthalmidae, rarely include specialist species; 5-Fleas exploiting a large host range, and taxonomically unrelated hosts, conform to highest abundance populations than specialist fleas, because they use a greater and more variable number of resources; 6-Large bodied and long lived mammals promote specialization in fleas, likely because these hosts represent stable and foreseeable resources; 7-fleas with a wide geographic range have low host specificity (Ezquiaga et al, 2020;Krasnov et al, 2004Krasnov et al, , 2005Sanchez & Lareschi, 2019;Schramm & Lewis, 1988;van der Mescht et al, 2017).…”

“…Generalized trends about specialization of mammal fleas were reported by several authors and can be summarized as: 1‐ specialist fleas parasitize mammals that are specialized on habit or structures; 2‐ specialist fleas at generic level parasitize monotypic genera host or host without sympatric congeners; 3‐ the majority of flea groups specialist of insectivore and marsupial hosts are either species‐specific or genus‐specific. In contrast, rodents are parasitized by few groups of specialist fleas; 4‐ the most diverse families of Siphonaptera, such as Stephanocircidae and Ctenophthalmidae, rarely include specialist species; 5‐ Fleas exploiting a large host range, and taxonomically unrelated hosts, conform to highest abundance populations than specialist fleas, because they use a greater and more variable number of resources; 6‐ Large bodied and long lived mammals promote specialization in fleas, likely because these hosts represent stable and foreseeable resources; 7‐ fleas with a wide geographic range have low host specificity (Ezquiaga et al, 2020; Krasnov et al, 2004, 2005; Sanchez & Lareschi, 2019; Schramm & Lewis, 1988; van der Mescht et al, 2017).…”