Wood Frog Life History 41 



place through the entire egg mass. If so, smaller clutch size resulting 

 from selective pressures for small egg mass size would be an inapprop- 

 riate hypothesis. 



The eggs of Alabama wood frogs are the largest reported for any 

 population of R. sylvatica (x = 2.9 mm diam., SD = .08, N = 50). Com- 

 parison of these values with previously published information indicates 

 a general trend for egg diameter to increase southward (Table 2.). 

 Berven (1982a) hypothesized that selection has acted primarily on egg 

 size, and that other reproductive traits such as clutch size, body size, 

 and age at first reproduction have evolved secondarily. Different selec- 

 tive pressures in different environments would confer differential selec- 

 tive advantages on particular sizes of eggs, clutches, and adults (see 

 Berven 1982a,b, for discussion). 



The large size of eggs in Alabama populations of R. sylvatica is 

 probably a consequence of increased fitness (larger size) of larvae hatch- 

 ing from these eggs (see Berven 1982a,b), a phenomenon that would 

 result in faster growth rates and shorter larval periods. In Alabama 

 populations, selection for rapid metamorphosis would probably result 

 from breeding exclusively in temporary ponds. An additional selective 

 pressure for more rapid metamorphosis in R. sylvatica may be the con- 

 current breeding of R. sphenocephala in the same sites. This does not 

 seem to be the case farther north. Berven's hypothesis concerning the 

 relationship of large egg size to large body size is difficult to support 

 with data from Alabama wood frogs. Although egg size is largest in 

 Alabama populations, adults are somewhat smaller than those reported 

 in other parts of the southern Appalachians (see earlier mention). 

 Because determination of different age classes was not possible during 

 this study, size comparisons and determinations of age and size at first 

 (and subsequent) reproduction await further study. Larger sample sizes 

 obtained by future workers will probably help to clarify this situation. 



The diameters of egg jelly envelopes for R. sylvatica in Alabama 

 are larger than values reported in other parts of the range. Diameters of 

 inner envelopes averaged 6.6 mm (R = 5.4 to 7.2 mm, N = 50); outer 

 envelopes averaged 14.0 mm (R = 12.4 to 17.3 mm, N = 50). Few data 

 are available on more northerly populations (Table 2). The reasons that 

 jelly envelopes of Alabama wood frogs are so much larger than those in 

 northern populations are not obvious. Perhaps jelly deposition is con- 

 trolled by egg size, with larger eggs receiving more jelly. 



Egg Fertility, Development, and Predation 



Fertility, although variable, was quite high, and several egg masses 

 exhibited 100% fertility. Three clutches were entirely infertile, perhaps a 

 result of oviposition in the absence of a clasping male. Early mortality 



