Damselfish face climate change: Impact of temperature and habitat structure on agonistic behavior

animal’s aerobic scope [45]. Thermal stress was already shown to cause behavioral changes that are usually followed by reduced ability to exploit resources [46], decreased immunity response [47,48], reproductive losses [6,49], and failure to recognize environmental cues [50,51]. A recent study on butterflyfishes showed reduced aggression due to reef’s complexity loss [4]. The dusky damselfish appears to tolerate some temperature variation: it can withstand acute temperature increase caused by seawater entrapped in small tide pools that can reach 36˚C (personal observation). However, their tolerance time-range seems to be narrow (i.e., only 4–6 hours of the low tide). In this scenario, fish seem to reduce locomotion and the per- centage of time invested in agonistic behaviors until the flow returns to higher levels, and the animals have access to the open sea. In contrast, the present study imposed a more extended period of high temperature (30 days), and S. fuscus tolerance zone may have been exceeded to enter the resistance zone. Warming caused a decrease in costly displays (threats, attacks) that were replaced by more economical ones, such as vigilance. Although fish spent more time close to the mirror (after mirror exposure), showing that warming did not affect the ability to Fig 4. Effects of temperature (28 and 34˚C) and habitat structure (complex and barren) on dusky damselfish behavior before and after mirror exposure.

Combinations of temperature and complexity with the same letter above the bars are not statistically significant after pairwise comparisons (p>0.05 in pairwise comparisons using permutation tests) (For details, see Tables 3 and 4). https://doi.org/10.1371/journal.pone.0235389.g004 Table 4. SIMPER results for the behaviors that most contributed to the differences observed after pairwise comparison for significant effects obtained in PERMANOVA. Behavior Before mirror After mirror 28 vs. 34 28C vs. 34C 28C vs. 34B 28B vs. 34B 34C vs. 34B Immobility 3rd (28) 3rd (34C) 4th (28C) 2nd (28B) 4th (34C) Vigilance 2nd (28) 4th (34C) 2nd (28C) 3rd (28B) 3rd (34C) Feeding 4th (28) Threat 1st (34) 2nd (28C) 1st (34B) 1st (34B) 1st (34B) Attack 1st (28C) 3rd (28C) 4th (28B) 2nd (34B) For each comparison between two conditions, behaviors were ranked in terms of contribution. The code in parentheses indicates the condition in which the behavior was more frequent: 28˚C, 34˚C, Complex–C or Barren—B. https://doi.org/10.1371/journal.pone.0235389.t004 PLOS ONE Temperature and habitat structure on damselfish behavior PLOS ONE | https://doi.org/10.1371/journal.pone.0235389 June 30, 2020 8 / 13