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Parental care and EGG size in salamanders: An examination of the safe harbor hypothesis
Author(s) -
Nussbaum Ronald A.
Publication year - 1987
Publication title -
population ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 59
eISSN - 1438-390X
pISSN - 1438-3896
DOI - 10.1007/bf02515423
Subject(s) - hatchling , biology , river ecosystem , paternal care , ecology , poecilia , zoology , fishery , habitat , fish <actinopterygii> , offspring , pregnancy , genetics , hatching
Summary The safe harbor hypothesis includes the suggestion that parental care causes the embryonic stage to be the safest harbor, and, therefore, egg size will increase in populations with parental care to decrease the duration of subsequent, higher risk stages. Neither the safe habor hypothesis nor r and K theory seem adequate to explain the correlation between egg size and the presence/absence of parental care among salamanders, a group in which there is a further correlation between the larval (hatchling) habitat and egg size/parental care. Pond‐breeding salamanders generally have small eggs and lack parental care, and stream‐breeding salamanders generally have large eggs and parental care. I argue that the fundamental difference in the food available to hatchling salamanders between lentic (plankton‐rich) and lotic (plankton‐poor) environments selects for relatively lower parental investment in the lentic environment. From the standpoint of parental fitness, small (more numerous) hatchlings have a greater payoff where the available food is mall and dense (zooplankton in lentic environments), and large hatchlings are selectively advantageous where the food is of large size and less dense (benthic invertebrates in lotic environments). Selection for larger hatchlings in lotic environments results in longer embryonic periods and, ceteris paribus , greater total embryonic mortality. Embryo hiding and guarding have evolved among lotic‐breeding salamanders as compensatory mechanisms to reduce the rate of embryonic mortality. In this view, parental care is a consequence of selection for larger egg size and not an umbrella that allows egg size to increase, contrary to the safe harbor hypothesis. The relationship between variance in parental investment and food available to offspring, developed here for salamanders, may be of general significance. Yosiaki Itô , a critic of r and K theory, independently arrived at a similar conclusion from a broader data base.