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Intra-sexual competition plays an important role in the evolutionary process of sexual selection. Male-male competition over resources that are essential for mating success may prevent unsuccessful competitors from breeding. The intensity of competition is influenced by the availability, quality, and distribution of such resources. The spatial distribution of resources may facilitate monopolisation, limit the density of breeders and skew the reproductive success among individuals in a population. In some species, one such resource is favourable nests sites, which males compete for, occupy and defend against intruders. The aim of this study was to test the extent to which nest spacing, and specifically inter-nest distance, induces intra-sexual competition (territorial aggression). In order to address this question I focused on how distance between pairs of nests affects nest occupancy, mating success and asynchrony in breeding of male two-spotted gobies (Pomatoschistus flavescens), a small fish with a resource defence based breeding system and uniparental care provided by males. Results show that shorter inter-nest distance did not affect nest occupancy, mating success or asynchrony in breeding of males and does not appear to intensify male-male competition. These results suggest that nest spacing does not limit the density of breeding males. However, further studies are required to understand the effect of nest spacing on the intensity of sexual selection. The high occupancy rates, irrespective of distance, suggest that the artificial nests are favourable nesting sites. Although potential natural nesting sites for the two-spotted gobies seem to be abundant in the studied area, high-quality nests might be in limited supply.

The gecko Mediodactylus kotschyi is considered rare in mainland Greece, yet it is very abundant on the Aegean islands. It has been thought to be saxicolous throughout much of its range. In a recent survey on the Peloponnese peninsula, however, we encountered it mainly on trees, and with higher frequency than previously reported. We combined our observations of localities in which we detected this gecko, and places where we failed to detect it, with data about its occurrence from the literature and museum collections. We posited two hypotheses as possible causes for the apparent relative scarcity of M. kotschyi in the Peloponnese: that it is associated with low precipitation and that it has an aversion to limestone rock. We predicted that M. kotschyi would be more likely to be found in arid places and where limestone is not the dominant type of rock, since it has been reported that this substrate is less suitable for this species. Moreover, we predicted that geckos occurring in limestone regions would be found on trees rather than under rocks. Geckos were indeed found mainly in the more arid parts of the Peloponnese, but not exclusively so. We found no evidence of limestone avoidance. We suggest that, because M. kotschyi is better known as being mostly saxicolous over most of its range, and exclusively so on the Greek islands, in the Peloponnese the search for this species has been restricted to a single habitat type, i.e. under rocks and not on trees. It may thus inhabit more localities in the Peloponnese and be more abundant there than has previously been thought., Acta Herpetologica, Vol 11 No 2 (2016)