Richard C. Bruce

Sexual Size Dimorphism in Desmognathine Salamanders

Salamanders of the genus Desmognathus show an unusual form of sexual size dimorphism in which males are younger and smaller than females at first reproduction but surpass females in body size as they age. Data are presented that document this relationship for D. ochrophaeus, D. monticola, and D. quadramaculatus. The explanation for sexual size dimorphism in Desmognathus may reside in reproductive features that yield differences between the sexes in the relationship between body size and reproductive success; in particular, in older individuals, the rate of increase in reproductive success with body size is probably less in females than in males.

Life-history perspective of adaptive radiation in desmognathine salamanders

This study investigates interspecific variation in age at first reproduction, fecundity, and body size in multispecies assemblages of desmognathine salamanders. The hypotheses tested are that interspecific differences in body size among desmognathines stem proximately from variation in age at first reproduction and that variation in the latter trait is positively correlated with variation in fecundity among species. It is shown that a correlation between age at first reproduction and fecundity, combined with a uniform rate of survival, based on available estimates of these parameters, will yield equivalent values of net reproductive rate (Ro) among the species of a given assemblage. Such equivalence represents a form of life-history symmetry. Data from two assemblages are presented in support of the argument for symmetry. Such life-history symmetry may reflect uniformity in morphological specialization in desmognathines. Given the morphological adaptations to burrowing (head-wedging) in the subfamily, the relationship between adult body size and habitat preference in Desmognathus may reflect adaptation to the size of cover objects and composition of the substratum along the aquatic-terrestrial habitat gradient. I propose that these variables, in association with predation and competition, represent the selective factors responsible for body size diversification in Desmognathus.

An ecological life table for the salamander Eurycea wilderae

clinid fish Ribeiroclinus eigenmanni with discussion of the intrarelationships and zoogeography of the Clinidae. Copeia 1970(3):430-436. STEPIEN, C. A. 1985. Life history, ecology, and regulation of the color morphic patterns of the giant kelpfish, Heterostichus rostratus Girard (family Clinidae). Unpubl. Ph.D. dissert., University of Southern California, Los Angeles, California. . 1986a. Regulation of color morphic patterns in the giant kelpfish: genetic versus environmental factors. J. Exp. Mar. Biol. Ecol. 100:181-208. 1986b. Life history and larval development of the giant kelpfish, Heterostichus rostratus Girard (family Clinidae). Fish. Bull. 84(4):809-826. 1987. Color pattern and habitat difference (Blennioidei: Clinidae) between male, female, and juvenile giant kelpfish. Bull. Mar. Sci. 41(1):45-58. WILKIE, D. W. 1966. Colour pigments in the penpoint gunnel Apodichthysflavidus and their ecological significance. Unpubl. M.S. thesis, University of British Columbia, Vancouver, British Columbia, Canada. WILLIAMS, G. C. 1954. Differential vertical distribution of the sexes in Gibbonsia elegans with remarks on two nominal subspecies of this fish. Copeia 1954(4):267-273.

Larval periods, population structure and the effects of stream drift in larvae of the salamanders Desmognathus quadramaculatus and Leurognathus marmoratus in a southern Appalachian stream

Non-destructive sampling of salamander larvae at East Fork Overflow Creek and its tributaries in the Blue Ridge Mountains of North Carolina provided information on larval life histories of Desmognathus quadramaculatus and Leurognathus marmoratus. Snout-vent length data indicated that both D. quadramaculatus and L. marmoratus have larval periods of three years, which is considerably longer than estimates provided by previous investigators. Individual growth rates were higher and metamorphic sizes larger in D. quadramaculatus than in L. marmoratus. In both species, first-year larvae were under-represented in the samples from East Fork Overflow Creek. Sampling in tributaries yielded higher frequencies of young larvae of D. quadramaculatus. These data suggested that in the latter species, reproduction was concentrated in headwater tributaries and that the downstream larval populations were constituted in part from stream drift. Although drift may thus account for the population structure of D. quadramaculatus, it does not explain similar findings for L. marmoratus, inasmuch as the latter species was nearly absent from the tributaries.

Larval Periods and Metamorphosis in Two Species of Salamanders of the Genus Eurycea

Larval periods and metamorphosis were studied in populations of Eurycea bislineata and E. longicauda guttolineata in the southern Blue Ridge Mountains of North Carolina. The basic data were snout-vent lengths of larvae collected in serial samples taken over one-year periods. The larval period of E. bislineata was about one year in the two populations studied, although growth rate was higher and metamorphic size was much greater in a pond population than in a stream population. The one-year larval phase contrasts with a 2-3 year larval period of E. bislineata in the northern United States. The difference is considered an adaptive response to larvae of other species of salamanders, which act as competitors or predators, and are more prevalent in the southern Blue Ridge. In two populations of E. longicauda guttolineata the larval period was normally 4-5 months, though larvae sometimes overwintered and metamorphosed after a larval period of 12-16 months. The generally brief larval phase of this species may represent an adaptation to temporary aquatic habitats, with overwintering a facultative means for slow-growing larvae to attain a larger metamorphic size when conditions are favorable for continued larval existence.

Egg-Laying, Larval Periods and Metamorphosis of Eurycea bislineata and E. junaluska at Santeetlah Creek, North Carolina

to elucidate the larval development of the two species, and to provide information on other life-history traits. Both species oviposit in May at Santeetlah Creek, with hatching following in June. The nesting sites are beneath large rocks in the stream channel and are similar in the two species. The larval period of E. bislineata is either one or two years, with the frequency of early metamorphosis apparently varying annually. In E. junaluska the larval period is two years, perhaps occasionally longer. The metamorphic periods of the two species overlap in late spring and early summer, although larvae of E.junaluska tend to metamorphose slightly later in the year. Larval growth rates are higher in E. junaluska than they are in E. bislineata, and the former completes metamorphosis at larger sizes.

Population Structure, Life History and Evolution of Paedogenesis in the Salamander Eurycea neotenes

de Vipera aspis dans la nature, p. 147-154. In: Distribution temporelle des activites animales et humaines. J. Medioni (ed.). Masson et Cie., Paris. NEWCOMER, R. T., D. H. TAYLOR AND S. I. GUTrMAN. 1974. Celestial orientation in two species of water snakes (Natrix sipedon and Regina septemvittata). Herpetologica 30:194-200. NOBLE, G. K. 1937. The sense organs involved in the courtship of Storeria, Thamnophis and other snakes. Bull. Amer. Mus. Nat. Hist. 73: 673-725. ,AND H. J. CLAUSEN. 1936. The aggregation behavior of Storeria dekayi and other snakes, with especial reference to the sense organs involved. Ecol. Monogr. 6:271-316. OSGOOD, D. W., AND P. D. WEIGL. 1972. Monitoring activity of small mammals by temperaturetelemetry. Ecology 53:738-740. PARKER, W. S. 1974. Comparative ecology of two colubrid snakes, Masticophis t. taeniatus (Hallowell) and Pituophis melanoleucus deserticola Stejneger, in northern Utah. Unpubl. Ph.D. Thesis. Univ. of Utah, Salt Lake City. ,AND W. S. BROWN. 1972. Telemetric study of movements and oviposition of two female Masticophis t. taeniatus. Copeia 1972:892-895. , AND . 1973. Species composition and population changes in two complexes of snake hibernacula in northern Utah. Herpetologica 29: 319-326. PLATT, D. R. 1969. Natural history of the hognose snakes Heterodon platyrhinos and Heterodon nasicus. Univ. Kans. Publ. Mus. Nat. Hist. 18:253-420. PRESTT, I. 1971. An ecological study of the viper, Vipera berus, in southern Britain. J. Zool. (Lond.) 164:373-418.

Reproductive Biology of the Mud Salamander, Pseudotriton montanus, in Western South Carolina

The reproductive biology of Pseudotriton montanus was studied for two populations in the Piedmont of western South Carolina. Males reached sexual maturity during the first year following metamorphosis, and attained breeding condition in their second, third or fourth summer of life, depending on the duration of the larval phase and on the season of metamorphosis. Males produced sperm annually, with evacuation of the testes beginning in late July and continuing through the autumn. All mature males taken from August through November had vasa deferentia packed with sperm. Females were found to oviposit initially in the autumn or winter at four or five years of age, and thereafter on an irregular schedule. Clutch size increased as a function of body size, and ranged from 77 to 192 eggs/female. In comparison with Pseudotriton ruber, P. montanus shows more rapid growth, earlier maturity and higher fecundity. Such a life-history strategy may be a consequence of r-selection in response to intrinsically hazardous and uncertain environments. It is proposed that the irregular female reproductive cycle of P. montanus is a facultative adaptation which prolongs life and provides for iteroparity under conditions of variable juvenile and constant adult mortality, yet allows for high fecundity, especially in the initial reproductive year, under overall conditions of r-selection.

Reproductive Biology of the Salamander Pseudotriton ruber in the Southern Blue Ridge Mountains

Life-history and reproductive characteristics were investigated in populations of Pseudotriton ruber in the southern Blue Ridge Mountains. Larvae metamorphose in late spring and early summer at ages of 31-33 months. Most males probably mature during the first year after metamorphosis, and breed initially in their fourth summer at an age of 45 months; some males may delay their first reproduction an additional year. Most females appear to reproduce initially at an age of five years or older, and thereafter on an annual schedule. Females mature at larger body sizes than males, and generally attain larger adult sizes. Adult males far outnumber females. Courtship and mating occur from late June through September, and females retreat to nesting sites for oviposition in early autumn, presumably remaining with their clutches until hatching in winter. Clutch size increases with female body size. A comparison of P. ruber and P. montanus suggests that life-cycle diversification within the genus has been accomplished through modification in rate phenomena associated with growth and reproduction; the differences are apparently related to adaptive divergence into northern upland (P. ruber) and southern lowland (P. montanus) environments.

Life Cycle and Population Structure of the Salamander Stereochilus marginatus in North Carolina

The life history of Stereochilus marginatus was studied at Croatan National Forest in eastern North Carolina. This highly aquatic salamander is abundant in drainage ditches, small ponds, and sluggish streams. Mating occurs in autumn, egg-laying in winter, and hatching in early spring. Although the usual length of the larval period is 25-28 months, some individuals apparently transform after a larval period of only 13-16 months. Larvae metamorphose in late spring and summer. The age range for initial reproduction in males is estimated as 21-45 months; however, most males develop to sexual maturity immediately after transformation, and breed initially at an age of 33 months. Most females remain immature during the year following metamorphosis, and oviposit for the first time at four years of age. Initial oviposition at three years of age may occur for females which metamorphose early and delay maturity, and for females which metamorphose late and develop to maturity immediately. There is no apparent sexual dimorphism, and the sex ratio is 1:1.