Testing for intraspecific and interspecific larval competition between two anurans: Hyla savignyi and Bufotes viridis

Intraspecific and interspecific competition can be important factors affecting anuran tadpoles in temporary pools. We focus on two co-occurring anuran species that are of conservation concern in Israel and may negatively interact: Bufotes viridis (Laurenti, 1768) and Hyla savignyi (Audouin, 1829). We conducted a replacement design mesocosm experiment to examine intraspecific and interspecific competition between tadpoles of these two species. Plastic tubs were assigned to five replacement design treatments: 0 Hyla + 20 Bufotes; 0 Hyla + 40 Bufotes; 20 Hyla + 20 Bufotes; 20 Hyla + 0 Bufotes; and 40 Hyla + 0 Bufotes, and a control with no tadpoles which was used to test for effects of the tadpoles on invertebrate community structure. While H. savignyi was significantly affected by intraspecific density, with smaller body mass and longer time to metamorphosis at the high-density treatment, B. viridis showed no intraspecific or interspecific density-dependent effects. However, B. viridis time to metamorphosis was negatively correlated with water temperature, while its survivorship was positively correlated with water temperature. The tadpoles affected neither abundance nor taxon richness of invertebrates. Our results suggest that stronger intraspecific competition than interspecific competition may contribute to the common co-occurrence of these two anurans in the same pools.