Ranging behavior drives parasite richness: A more parsimonious hypothesis

Abstract

Parasitism is a ubiquitous interspecific interaction that may play an important role in the evolution of hosts and parasites, molding many aspects of their behavior and ecology. Detecting behavioral changes of hosts infected with parasites is not a straightforward task. Extrapolating from individual-level responses to group-level decision-making is still a much more complex challenge. The ranging behavior of hosts that live in social groups is a good example. Many hypotheses of the cause-effect relationship between this behavior and parasite diversity and load have been proposed. For instance, Brockmeyer et al. [2015, Am. J. Primatol. 77:1036-1048] recently suggested that the richness of protozoan parasites influences the daily path length of free-ranging mandrills. We believe that this explanation for the relationship contains several implicit assumptions. Therefore, we offer an alternative, more parsimonious hypothesis in which daily path length is the driver of parasite richness rather than its consequence. Our hypothesis only assumes that ranging farther exposes animals to a richer parasite diversity. We discuss the data required to test these alternative hypotheses and recall empirical evidence and theoretical modeling results supporting or rejecting their assumptions. We also propose a model of the expected outcomes in terms of species richness, load, intensity of infection, and within-group community similarity of non-lethal environmentally transmitted parasites in social animal groups showing distinct patterns of range use. Am. J. Primatol. 78:923-927, 2016. © 2016 Wiley Periodicals, Inc.

Does elevated parasite richness in the environment affect daily path length of animals or is it the converse? An answer bringing some new elements of discussion.

“…In 2015, Brockmeyer et al [2] suggested that mandrills (Mandrillus sphinx) may accept additional ranging costs to avoid heavily parasitized areas. Following this paper, Bicca-Marques and Calegaro-Marques [1] questioned this interpretation and presented other hypotheses.…”

“…To summarize, whilst Brockmeyer et al [2] proposed that elevated daily path length may be a consequence of elevated parasite richness, Bicca-Marques and Calegaro-Marques [1] viewed it as a cause. In this current paper, Charpentier and Kappeler [3] respond to some of the criticisms by Bicca-Marques and Calegaro-Marques and discuss the putative parsimony of the two competing scenarios.…”

Batracobdella leeches, environmental features and Hydromantes salamanders

“…Salamander flanks and limbs seem to be the body parts where leeches more frequently attached (chi-squared test; χ 2 5 = 38.03, P < .001), while they are rarely observed on the belly. We suspect that leeches seldom remain on the ventral body parts of the salamanders, which generally remain in contact with the substrate ( Bicca-Marques and Calegaro-Marques, 2016 ). We observed a higher proportion of parasitized salamanders in cave areas near the surface where prey availability for salamanders is higher ( Ficetola et al, 2013 , Manenti et al, 2015 , Lunghi et al, 2017 ).…”

A reply to “Ranging Behavior Drives Parasite Richness: A More Parsimonious Hypothesis”

“…By not acknowledging the main focus of our paper and the preliminary nature of the analysis of the group's ranging behavior, which was yet clearly stated, Bicca-Marques and Calegaro-Marques (2016) have created, in our view, a heavily distorted point of departure for their article. In addition, Bicca-Marques and Calegaro-Marques (2016) failed to mention that we also proposed an alternative interpretation of the observed relationship based on an interaction between food availability and parasite load. Thus, we resent the impression that the incomplete and biased depiction of our article by Bicca-Marques and Calegaro-Marques (2016) may have created confusion in readers unfamiliar with the original study.…”

“…Thus, we resent the impression that the incomplete and biased depiction of our article by Bicca-Marques and Calegaro-Marques (2016) may have created confusion in readers unfamiliar with the original study. Bicca-Marques and Calegaro-Marques (2016) proposed that our interpretation of the observed positive relationship between daily path length (DPL) and parasite richness at the group level was based upon four implicit assumptions (detailed below). We think that the way these assumptions have been discussed is incomplete and deserving of additional comments.…”