Assessing symbiont extinction risk using cophylogenetic data

Abstract

Symbionts have a unique mode of life that has attracted the attention of ecologists and evolutionary biologists for centuries. As a result of this attention, these disciplines have produced a mature body of literature on host-symbiont interactions. In contrast, the discipline of symbiont conservation is still in a foundational stage. Here, we aim to integrate methodologies on symbiont coevolutionary biology with the perspective of conservation. We focus on host-symbiont cophylogenies, because they have been widely used to study symbiont diversification history and contain information on symbiont extinction. However, cophylogenetic information has never been used nor adapted to the perspective of conservation. Here, we propose a new statistic, "cophylogenetic extinction rate" (Ec), based on coevolutionary knowledge, that uses data from event-based cophylogenetic analyses, and which could be informative to assess relative symbiont extinction risks. Finally, we propose potential future research to further develop estimation of symbiont extinction risk from cophylogenetic analyses and continue the integration of this existing knowledge of coevolutionary biology and cophylogenetics into future symbiont conservation studies and practices.

Host diversity outperforms climate as a global driver of symbiont diversity in the bird‐feather mite system

“…Therefore, considering future climate change scenarios that indicate an increased occurrence of extreme precipitation values (including more frequent droughts) and rising temperature conditions may cause species extinction within this group (Carlson et al, 2017;Fischer & Knutti, 2015). In contrast, the small overall influence of abiotic factors on mite diversity suggests that the colonization of new hosts may not be hampered in the event of climate change (Doña & Johnson, 2020). However, our results also indicate that climate may play an important role, mainly in temperate regions.…”

“…These two aspects may be affected by ecological and evolutionary factors, such as species dispersal capabilities (Cizauskas et al, 2017;Doña & Johnson, 2020), level of specialization (Strona & Fattorini, 2016), host specificity (Fecchio, Wells, et al, 2019;Koh et al, 2004), host characteristics (e.g., evolutionary history: Colwell, Dunn, et al, 2012) and community characteristics, such as species richness (Koh et al, 2004). Among these factors, host-switching dynamics has received considerable attention because it can aid some symbionts to avoid extinction (Brooks & Hoberg, 2007;Carlson et al, 2017;Cizauskas et al, 2017;Doña & Johnson, 2020). Specifically, symbionts with higher colonization capabilities tend to be more generalist and may be less impacted by climate conditions changes because they may escape unsuitable conditions by reaching new hosts (Doña & Johnson, 2020).…”

“…Among these factors, host-switching dynamics has received considerable attention because it can aid some symbionts to avoid extinction (Brooks & Hoberg, 2007;Carlson et al, 2017;Cizauskas et al, 2017;Doña & Johnson, 2020). Specifically, symbionts with higher colonization capabilities tend to be more generalist and may be less impacted by climate conditions changes because they may escape unsuitable conditions by reaching new hosts (Doña & Johnson, 2020). However, symbionts with lower dispersal capabilities have lower opportunities to reach new hosts, tend to be less generalist, and thus most of their attempts to switch hosts fail (Doña & Johnson, 2020;Poulin, 2011).…”

“…Specifically, symbionts with higher colonization capabilities tend to be more generalist and may be less impacted by climate conditions changes because they may escape unsuitable conditions by reaching new hosts (Doña & Johnson, 2020). However, symbionts with lower dispersal capabilities have lower opportunities to reach new hosts, tend to be less generalist, and thus most of their attempts to switch hosts fail (Doña & Johnson, 2020;Poulin, 2011). In addition, these specialist symbionts might be particularly sensitive to certain abiotic factors (e.g., humidity), and if so, climate change may reduce even further the possibilities of successful colonization and thus increase symbiont extinction rates (Bush et al, 2013).…”

The ghost of hosts past: impacts of host extinction on parasite specificity

“…Parasites play critical roles in ecological communities through impacts on host populations and structuring food webs [7,8]. However, in comparison with their hosts, parasite extinctions are notoriously difficult to observe [9], though some can be inferred through analysis of ancient samples [10,11], or through co-phylogenetic analyses [12]. Beyond direct observation, the coextinction of parasites along with the loss of their hosts [13] has been studied via comparative analyses of threatened and non-threatened hosts [14,15], and simulations that identify likely coextinctions resulting from future host extinctions [3,[16][17][18][19].…”