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SIZE‐FECUNDITY RELATIONSHIPS AND THEIR EVOLUTIONARY IMPLICATIONS IN FIVE DESMOGNATHINE SALAMANDERS
Author(s) -
Tilley Stephen G.
Publication year - 1968
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1968.tb03479.x
Subject(s) - fecundity , biology , citation , genealogy , library science , sociology , demography , computer science , history , population
The plethodontid salamander genus Desmognathus comprises seven species according to current taxonomy, of which six occur in, and four are endemic to the Appalachian Mountain system of eastern North America. Over most of the southern Blue Ridge Physiographic Province several of these forms may exist sympatrically. An apparent maximum of sympatry occurs in the Balsam Mountains of southwestern Virginia, where five species, D. quadramaculatus, D. monticola, D. fuscus, D. ochrophaeus, and D. wrighti occur in abundance. Organ (1961) studied the ecological relationships and population dynamics of these species at Whitetop Mountain and Mt. Rogers in the Balsam Mountains. Hairston (1949) compared the ecologies of D. quadramaculatus, D. monticola, D. ochrophaeus, and D. wrighti in the Black Mountains of North Carolina where those four forms occur sympatrically. Both authors found that, in the order given above, these species form a series in which decreasing size is paralleled by an increasing tendency toward terrestrial habits. Organ further found that the trend is also paralleled by increasing juvenile survivorship. He concluded that heavier juvenile mortality is associated with aquatic sites, and that D. quadrarnaculatus, D. monticola, D. fuscus, D. ochrophaeus, and D. wrighti represent an evolutionary trend in which selection has favored progressively more terrestrial habits. Size and egg production are positively correlated in the genus Desmognathus, as they are in many animals. Organ (1961) also emphasized that the larger species lay larger clutches than the smaller ones, and that the evolutionary trend within the genus has been "the gradual transformation of a population with a high egg production and low survival into a population with low egg production and a high survival to maturity." He found no differences in number of clutches per year or age at maturity that might compensate for differences in clutch size. This paper attempts to further explore and compare the relationships between size and fecundity among the five sympatric species of Desmognathus and to elaborate on the hypotheses drawn by Organ relative to evolutionary trends in reproductive habits. In particular I have sought to determine whether fecundity differences among the five species are explained simply by differences in their sizes, or whether sizefecundity relationships are more complex.