Purpose to examine habitat partitioning in three species of salamanders. Materials




Дата канвертавання25.04.2016
Памер44.67 Kb.

Species packing in dusky salamanders


PURPOSE


  • To examine habitat partitioning in three species of salamanders.

MATERIALS


Aquatic nets

Buckets, jars, or bags

Data sheets

Paper towels


Introduction


Members of the salamander genus Desmognathus (Phylum Chordata, Class Amphibia, Order Urodela, Family Plethodontidae) are found most commonly in or near mountain streams, springs, or seeps, but are usually absent from larger streams or rivers where predatory fish occur. Like other members of the family Plethodontidae, dusky salamanders lack functional lungs. Gas exchange is primarily through the moist skin and mouth cavity. The lungless condition is thought to be an adaptation to mountain streams. The lung created buoyancy and made them more likely to be washed downstream from their territories; floating may also have made them more susceptible to predation.

These salamanders reach their greatest abundance in the southern Appalachian region where they probably evolved some 40 million years ago (Dunn 1926) or even earlier. In this region, members of the genus occur together in combinations of 3, 4, or 5 species. They are usually thought of as stream-bank salamanders, but individually the species vary from being mostly aquatic (D. quadramaculatus), through the “typical” stream bank habitat (D. monticola and/or D. fuscus), to mostly terrestrial (D. ochrophaeus) and fully terrestrial (D. wrighti and D. aeneus). Only D. quadramaculatus, D. monticola, and D. ochrophaeus occur in our study area.

All three of these species lay their eggs in or near water, and the female remains with them until they hatch 2 or 3 months later. All three have aquatic larval stages with external gills. The duration of the larval stage varies among these species from a few weeks to 2 years (Hairston 1984). After metamorphosis, individuals of all three species remain close to the stream in which they hatched.

All three species also feed largely on arthropods (larvae and adults) and worms. Their body mechanics being very similar, all three feed close to the ground. Like most amphibians, all three species are also nocturnal. Thus, there is much overlap in their fundamental niches (Hairston 1964, 1973; Krzysik 1979).

In this field study, we will attempt to determine how these three similar species have partitioned their common resource. There is one complicating factor: The larger salamanders may also feed on the smaller ones. Therefore, predation may also be a factor determining the distribution (zonation) of these salamanders about their stream habitat (Tilley 1968, Hairston 1984).

The Species


All Desmognathans have relatively short and stout bodies with hindlegs larger than forelegs (they can jump several times their body length to escape capture). There is usually a pale diagonal line from each eye to the angle of the jaw (Conant 1975).

Desmognathus quadramaculatus — the Black Bellied Salamander


D. quadramaculatus is a large (10-17 cm), robust salamander (Conant 1975). Their tails are very stout at the base, but measure less than one half of the total body length, and they are knifed-edged above. The belly is black in adults, while usually dark but flecked with yellow in young (put your specimen in a bottle to see its underside). There is usually a conspicuous double row of light dots along each side of the body.

This salamander, the heaviest and bulkiest of the lungless group, is daring enough to occasionally pause in the open on a wet rock, even in sunshine, although they usually hide beneath rocks during the day. When disturbed, they plunge beneath a nearby stone or swim vigorously away (with or against the current). Trying to catch these agile amphibians is like going fishing with your bare hands.


Desmognathus monticola — the Seal Salamander


D. monticola is also a stout-bodied salamander, but adults are substantially smaller (8-13 cm) than the Black-Bellied species (Conant 1975). Its tail is compressed and knife-edged above near the tip and measures approximately ½ of the total body length. Most specimens are boldly patterned above, but plain and quite pale below with a distinct lateral separation between dorsal (back) and ventral (belly) pigmentation. The back has strong black or dark brown markings on a ground of buff, gray, or light brown. The markings are extremely variable. Some specimens simply have scattered dark or light spots or streaks, and in the south, adults may lose virtually all traces of pattern. The belly is white in juveniles, becoming lightly and usually uniformly pigmented with gray or brown in old adults. Sometimes there is a single row of light dots on the sides between the legs. Old adults may be purplish brown, with dark markings few and obscure.

At night, poised at the entrance to a burrow or perched atop a wet rock and illuminated by the observer’s flashlight, its appearance suggests a miniature seal, hence the common name.


Desmognathus ochrophaeus — the Mountain Dusky Salamander


D. ochrophaeus is medium-sized (7-10 cm) with a round tail (Conant 1975). The tail is about half the total body length and as wide or even wider than its height at the base. This salamander is extraordinarily variable in coloration and pattern. Most have a wavy or irregular dorsal (back) stripe, and they may be marked with large areas that are remnants or light spots set in paired or zigzag fashion down the backs of the juveniles. More terrestrial than most other dusky salamanders, they sometimes wander far out into the woods during wet weather.

Field Procedure


The focus of collecting will be on the stream bank, but will extend from the stream proper into the surrounding forest. Students will work together in teams to complete this exercise. Each team will be issued a plastic collecting bag; paper towels to be moistened, fluffed, and inserted into the bag; a tape measure to determine the distance of a collection from the stream; and a data sheet to be inserted inside the collecting bag upon completion of the exercise.

1. To insure that all areas get sampled, teams will be assigned to particular areas.


  • One group will “fish” the stream itself, another will comb the stream bank and nearby “shore”, and the third group will search in the adjacent forest.

  • Some overlap in search areas is desirable.

  • Rotate groups to account for variation in collecting ability.

2. Sample the assigned areas for the presence of salamanders.


  • Rocks, logs, etc., should be turned by hand (and returned to their original positions after sampling).

  • You should expect that there will be many that “got away”. Keep track of how many.

3. Collecting technique


  • Use nets, if available, for collecting in the stream. Position the net downstream from a rock, lifting the rock from that end.

  • Otherwise, specimens should be captured by hand and transferred to a bucket, jar, or bag for identification.

  • Desmognathus species do not secrete any known odorous, slimy, or harmful chemicals (that’s why they make good fish bait) and can be handled without concern to the collector.

  • Try not to handle them excessively; besides mechanical injury, your body heat and the dryness of air may cause the salamander physiological stress.
  1. Record field data


  • Measure the distance of the catch from the nearest running water (not pools or seeps) and record on your data sheet being certain to identify units (inches, feet, meters). Critical boundaries include: in or out of water, < or > 1 ft., < or > 5 ft., and < or > 20 ft.

  • Note the type of cover under which the animal was located and any unusual circumstances associated with its behavior and/or capture.

  • Attempt to distinguish this salamander from others placed in the same bag on the basis of coloration or pattern, snout/vent or snout/tail length, deformities, etc. Record your description on the data sheet.
  1. Do not release adult specimens


  • This is to avoid repeated capture of some specimens.

  • Salamanders will be released when the exercise is completed.
  1. Larvae can be released without recording.


  • Larvae have feather-like external gills in the neck region.

  • Since larvae are aquatic in all three species, it is not possible to partition the habitat in any way we can determine in this exercise (it is also next to impossible to tell them apart).

ACKNOWLEDGEMENTS


The conceptual basis, design, and methodology of this laboratory exercise were adapted from the works of N. G. Hairston, as cited below and as practiced with graduate students at both the University of Michigan, Ann Arbor, and the University of North Carolina, Chapel Hill. His permission and encouragement to develop this lab at the undergraduate level are greatly appreciated.

literature cited and other references


Conant, Roger. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America (Peterson Field Guide Series). Houghton Mifflin Company, Boston, MA. Brevard College Call Number: 597.6 C743f

Dunn, E. R. 1926. Salamanders of the Family Plethodontidae. Smith College Anniversary Series, Vol. 7, Northhampton, MA. Brevard College (Moore Science) Call Number: 597.9 D923s

Glesener, Robert R. Salamanders of Moore Cove and Transylvania County. Unpublished PowerPoint presentation available on Brevard College Public Folders Intranet.

Hairston, N. G. 1964. Studies on the organization of animal communities. Journal of Animal Ecology 33(Supplement): 227-239.

———. 1973. Ecology, selection, and systematics. Breviora 414: 1-21.

———. 1980. Species packing in the salamander genus Desmognathus: what are the interspecific interactions involved? American Naturalist 115:354-366.

———. 1984. Inferences and Experimental Results in Guild Structure, in D. R. Strong, D. Simberloff, L. G. Abele, and A. B. Thistle (Eds.), Ecological Communities: Conceptual Issues and the Evidence. Princeton University Press, Princeton, NJ. Brevard College (Moore Science) Call Number: 574.5247 E19

———. 1987. Community Ecology and Salamander Guilds. Cambridge University Press, Cambridge. (See Chapter 6) Brevard College (Moore Science) Call Number: 597.65 H153c

Krzysik, A. J. 1979. Resource allocation, coexistence, and the niche structure of a streambank salamander community. Ecological Monographs 49(2): 173-194.

Martof, B. S., W. M. Palmer, J. R. Bailey, and J. R. Harrison III. 1980. Amphibians and Reptiles of the Carolinas and Virginia. University of North Carolina Press, Chapel Hill. Brevard College Call Number: 598.10975 A526

Tilley, S. 1968. Size-fecundity relationships and their evolutionary implications in five desmognathine salamanders. Evolution 22:806-816.

Exercise — Species Packing in Salamanders

NAME SECTION # DATE TIME BEGIN ______



GROUP BAG # TIME END


Specimen

Number

Description of

Salamander


Distance

(inches)

Describe

Location

Possible

Species

1













2













3













4













5













6













7













8













9













10













11













12













Main Foraging Zones: Number of escapes (“ones that got away”) _____

  • In stream (0 feet)

  • > 0 feet but <= 1 foot

  • > 1 foot but <= 5 feet

  • > 5 feet but <= 20 feet

  • > 20 feet

Copyright © Dr. Robert R. Glesener


База данных защищена авторским правом ©shkola.of.by 2016
звярнуцца да адміністрацыі

    Галоўная старонка