Linking animal contests and community structure using rockpool fishes as a model system

Abstract

Summary Competition for limiting resources is a fundamental and well‐established driver of niche partitioning, which in turn promotes species coexistence and biodiversity. Although contests are a well‐known behavioural mechanism by which organisms compete over limiting resources, there has been surprisingly little application of contest theory to understanding interspecific interactions, niche partitioning, species coexistence and biodiversity. We investigated the link between contest dynamics and community structure using two intertidal rockpool fishes, Bathygobius cocosensis (Gobiidae) and Lepidoblennius haplodactylus (Tripterygiidae), as model species. We assessed the abundance and distribution of the two species on intertidal rocky shores of South‐East Australia, and whether distribution patterns were related to abiotic variables. We then conducted interspecific contest experiments between pairs of B. cocosensis and L. haplodactylus of varying size and sex under high and low dissolved oxygen levels to assess the competitive dominance of the species. To relate these results to community structure, we quantified temporal patterns of rockpool fidelity of each species in situ. Field surveys revealed that B. cocosensis was most prevalent in rockpools with higher dissolved oxygen, and L. haplodactylus was most prevalent in rockpools that contained no B. cocosensis. Contest experiments revealed that B. cocosensis displayed higher resource holding power than L. haplodactylus regardless of size asymmetry, sex or dissolved oxygen concentration, although contest intensity was influenced by relative body size of competing individuals. Furthermore, the microhabitat preference of L. haplodactylus was modulated in the presence of B. cocosensis. In the field, B. cocosensis displayed higher rockpool fidelity than L. haplodactylus. In light of these findings, we propose that B. cocosensis is the superior competitor but persistence of both species is likely facilitated by low‐cost contest resolution strategies, plasticity in microhabitat preference, negative spatial co‐variation and interspecific variation in dispersal and corresponding home range sizes. By using contest theory to understand the dynamics of interspecific contests, insight has been gained into how habitat is partitioned, species coexist and ultimately how biodiversity is maintained. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12859/suppinfo is available for this article.

Size, sex and social experience: Experimental tests of multiple factors mediating contest behaviour in a rockpool fish

“…Water was maintained at a pH of 8.5–8.6, a temperature of 22°C and a salinity level of 38–40 PSU. In the centre of each aquarium, a small rock (approximately 50 cm 2 ) that had been collected from the rocky shore was placed on small tiles to elevate it above the gravel to form a shelter (Paijmans & Wong, ). Fish were fed with thawed frozen brine shrimp daily.…”

“…While many contest studies have utilised fish as a model species to study elements of contest behaviour, the majority have focused on freshwater species (Beaugrand & Beaugrand, ; Chellappa et al, ; Cutts, Brembs, Metcalfe, & Taylor, ) with few focusing on marine species (Grossman, ). Further, fewer studies have focused on intertidal fish species (Paijmans & Wong, ) which is surprising given the interest in understanding factors governing community structure of intertidal organisms (Barjau‐González, Romo‐Piñera, López‐Vivas, Pérez‐Castillo, & Milicua, ; Kanamori, Fukaya, & Noda, ; Sorte et al, ). In the present study, the marine intertidal fish, Bathygobius cocosensis (Gobiidae), was used as a model species.…”

“…B. cocosensis is a highly abundant and numerically dominant species found along the south‐east Australian coastline (Griffiths, ). This species permanently resides within rockpools during its entire life cycle (Griffiths, West, Davis, & Russell, ), utilises rocks as shelter, and exhibits aggressive and territorial behaviours (Griffiths, ; Paijmans & Wong, ). It is supposed that the sexes are likely to behave differently in terms of competition over shelter, given that males likely defend eggs laid by females in the rocks (Tavolga ).…”

Thermal adaptation and acclimation in an intertidal goby (Bathygobius cocosensis)

“…Bathygobius cocosensis vary in their morphology depending on whether they inhabit the low-tide or high-tide zone, with those from high-tide rock-pools being smaller on average and with eyes further up their heads (potentially for better vision of avian predators) (Malard et al 2016). Bathygobius cocosensis is an aggressive and territorial species (Paijmans and Wong 2017), and competition for food and habitat is intense particularly in the low-tide zone where there is better access to food and refuges. to match the background colour.…”

“…Rapid growth can reduce mortality rates, by reducing time spent in the pelagic larval phase, and large settlement sizes often increase post-metamorphic survival ) and potentially competitive ability. Bathygobius cocosensis are an aggressive species, and larger individuals have been observed to inhabit rock-pools in the low-tide region of the intertidal zone (Malard et al 2016;Paijmans and Wong 2017), which generally provide greater access to food and refuges. Thia et al (2018) found that individuals of B. cocosensis that settle at a small size remain small for at least four days post-settlement, and larger B. cocosensis adults have also been observed to have higher routine metabolic rates than smaller individuals and faster burst swimming speeds (da Silva et al 2019a).…”