The effects of phylogeny, habitat and host characteristics on the thermal sensitivity of helminth development.

Samraat Pawar,Péter K Molnár,Juan S Vargas Soto,Janet Koprivnikar,Daniel P Benesh,Jessica Ann Phillips

doi:10.1098/rspb.2021.1878

Abstract

Helminth parasites are part of almost every ecosystem, with more than 300 000 species worldwide. Helminth infection dynamics are expected to be altered by climate change, but predicting future changes is difficult owing to lacking thermal sensitivity data for greater than 99.9% of helminth species. Here, we compiled the largest dataset to date on helminth temperature sensitivities and used the Metabolic Theory of Ecology to estimate activation energies (AEs) for parasite developmental rates. The median AE for 129 thermal performance curves was 0.67, similar to non-parasitic animals. Although exceptions existed, related species tended to have similar thermal sensitivities, suggesting some helminth taxa are inherently more affected by rising temperatures than others. Developmental rates were more temperature-sensitive for species from colder habitats than those from warmer habitats, and more temperature sensitive for species in terrestrial than aquatic habitats. AEs did not depend on whether helminth life stages were free-living or within hosts, whether the species infected plants or animals, or whether the species had an endotherm host in its life cycle. The phylogenetic conservatism of AE may facilitate predicting how temperature change affects the development of helminth species for which empirical data are lacking or difficult to obtain.

Highlights

Parasitic helminths are an integral part of almost every ecosystem [1] and can be key drivers of the population dynamics of their hosts and of the food webs in which they are embedded [1,2,3,4]
Helminth infection dynamics are expected to be altered by climate change, but predicting future changes is difficult owing to lacking thermal sensitivity data for greater than 99.9% of helminth species
We considered the current rather than the ancestral distribution of parasites because this probably reflects their potential thermal tolerance, and determining the endemic range would not be possible for most species; (v) parasite life cycle: we recorded the life stage at the beginning and end of each development experiment; (vi) free-living or in host: we categorized experiments by whether the focal parasite stage was free-living in the environment or in a host

Summary

Introduction

Parasitic helminths (i.e. acanthocephalans, cestodes, nematodes and trematodes) are an integral part of almost every ecosystem [1] and can be key drivers of the population dynamics of their hosts and of the food webs in which they are embedded [1,2,3,4]. Given that the vast majority of helminths have at least one life stage that is free in the environment and/or rely on an ectotherm intermediate host for progression to the life stage, climate warming is expected to alter helminth-host interactions around the globe [7,8]. Predicting such impacts is critical for proactive ecosystem management and public health planning [9], but such endeavours are complicated by a lack of data on the thermal sensitivity of greater than 99.9% of all helminth species [10]. To our knowledge, we compiled the largest dataset on helminth thermal performance to date, and evaluated whether the thermal sensitivity of development varied with 2 phylogeny, characteristics of the host–parasite system, and/ or environmental features

Methods

Results

Findings

Discussion