But also three main groups can be detected, one of them with the highest Tipifarnib chemical structure microhabitat temperatures and thermal tolerances, which is integrated by lowland species, collected from 430m to 827m altitude, another with intermediate microhabitat temperatures and embryonic thermal tolerances, with species collected at 1200m altitude, and finally a third group with the lowest microhabitat temperatures and thermal tolerances, which has the two highland species collected at 2600m altitude. Thus, a decrease of the environmental temperature along an altitudinal gradient is in concordance with a decrease in the embryonic thermal tolerance. These results, therefore, show the thermal adjustment or thermal adaptation sensu lato between the embryonic thermal tolerances and the altitudinal distribution of the anuran species.
Previous studies have found a correlation between the thermal tolerances of anuran embryos and their geographic distribution [1, 21�C24], but there are not reports along altitudinal gradients. Other works have found this altitudinal relationship in adults, however, with the methodology of the critical thermal maximum (CTMax) and critical thermal minimum (CTMin) proposed by Hutchison [25], Heatwole et al. [26], and Lutterschmidt and Hutchison [27]. For instance, Christian et al. [28] reported that E. portoricensis located at 700m altitude had a lower CTMin than E. coqui found at 15m altitude. Also, Spellerberg [29], and Huang et al. [30], working on lizards from Australia and Taiwan, respectively, established that species from high altitudes had a lower critical temperatures than species from lowland places.
Other studies have found this inverse relationship between the CTMax and altitude for amphibian populations from temperate zones [5, 31�C33] but not for tropical species of Puerto Rico, such as tadpoles of Leptodactylus albilabris [34] and adults of Eleutherodactylus coqui [28].Thermal adjustments of anuran embryos can be also detected in relation to different microhabitat temperatures at the same altitude. For instance, D. truncatus is a lowland species with terrestrial embryos which develop in a sheltered microhabitat with little variation of the environmental temperature (Table 2) and has a narrower thermal tolerance range than embryos of other species of the same locality (H. crepitans and D.
microcephalus, Figures 1(c) and 1(d)), which develop on the surface of waters exposed to intense sunny days and cold nights. Another example is registered in the two sympatric study species with foam nests. Embryos of E. pustulosus develop in foam nest floating on water in open areas and have AV-951 a wider microhabitat temperatures and thermal tolerances than embryos of L. insularum (Figures 1(f) and 1(g)), which develop in shaded places [35]. 4.2.