Interspecific competition in bats: state of knowledge and research challenges

Abstract

1. Interspecific competition (IC) is often seen as a main driver of evolutionary patterns and community structure. Bats might compete for key resources, and cases of exaggerated divergence of resource-related characters or trait overdispersion in bat assemblages are often explained in terms of current or past interspecific competition. However, other pressures leading to patterns that mimic the outcome of competition cannot always be ruled out. 2. We present the state of knowledge on IC among bats, providing a critical evaluation of the information available and identifying open questions and challenges. 3. We reviewed 100 documents addressing potential or actual IC in bats and categorised them in terms of the resource for which bats compete (food, foraging habitat, roosts, water, and acoustic space). We also examined the ecomorphological and behavioural traits considered therein to highlight responses to IC or niche partitioning. 4. We found that: although resources should be limiting in order for competition to occur, this is seldom tested; sympatry is sometimes taken as synonymous of syntopy (yet sympatric species that are not syntopic will never experience competition); comparisons between sympatry and allopatry are rare; and testing of objective criteria exploring the existence of niche partitioning or character displacement is not commonly adopted. 5. While morphological examination of food remains in droppings has often led to coarse-grained analysis that proved insufficient to establish the occurrence of food niche overlap or partitioning, new frontiers are being opened by state-of-the-art molecular dietary analysis. 6. A better understanding of IC in bats is paramount, since distributional changes leading to novel bat assemblages driven by climate change are already taking place, and the dramatic decline in insect availability, as well as the global loss or alteration of foraging habitat, may generate new competitive interactions or exacerbate existing interactions in the Anthropocene, and into the future.

Artificial light may change flight patterns of bats near bridges along urban waterways

“…Among the most prevalent sources of change in biodiversity state, Artificial Light At Night (ALAN) is increasingly recognized as a new threat (Koen et al, 2018). ALAN impacts a wide range of taxa, from individual physiological response to ecosystem functioning, interactions between species and regulatory processes (Hölker et al, 2010;Knop et al, 2017;Bennie et al, 2018;Salinas-Ramos et al, 2020) at many spatiotemporal scales (Altermatt & Ebert, 2016;Gaston et al, 2017).…”

Trophic resource partitioning drives fine-scale coexistence in cryptic bat species

“…It has been previously hypothesized that arthropods are abundant and do not constitute a limiting resource for bats (Arlettaz, 1999;Krüger et al, 2014). However, exclusion experiments in both tropical (Kalka et al, 2008) and temperate forests (Böhm et al, 2011) show that bats can control the abundance of arthropods, and therefore, arthropods could be a limiting resource to competitors (Salinas-Ramos et al, 2020).…”

“…This framework has been often used as a null model to evaluate whether observed patterns deviate from neutral expectations (Alonso et al, 2006;McGill et al, 2006). Yet, some studies of mobile organisms have failed to identify evidence of resource partitioning (e.g., Luiselli, 2008), suggesting that in some cases biotic interactions only play a minor role in governing community assembly, perhaps because resources are not limiting (Salinas-Ramos et al, 2020), and therefore, neutral processes likely play a more important role.…”

Trophic resource partitioning drives fine‐scale coexistence in cryptic bat species

“…This framework has been often used as a null model to evaluate whether observed patterns deviate from neutral expectations (Alonso et al., 2006; McGill et al., 2006). Yet, some studies of mobile organisms have failed to identify evidence of resource partitioning (e.g., Luiselli, 2008), suggesting that in some cases biotic interactions only play a minor role in governing community assembly, perhaps because resources are not limiting (Salinas‐Ramos et al., 2020), and therefore, neutral processes likely play a more important role.…”

“…However, the majority of coexistence studies focus on only sympatric populations, preventing an evaluation of how the presence of a competitor may change resource use, thus limiting the power of inferences (Salinas‐Ramos et al., 2020). Moreover, most studies also focus on diet only, and disregard prey selection relative to prey availability or resource limitation (Salinas‐Ramos et al., 2020). Accounting for prey selection (e.g., Rytkönen et al., 2019) can provide a more complete picture of consumer trophic preferences (Lawlor, 1980).…”