Sex ratio allocation has important fitness consequences, and theory predicts that parents should ... more Sex ratio allocation has important fitness consequences, and theory predicts that parents should adjust offspring sex ratio in cases where the fitness returns of producing male and female offspring vary. The ability of fathers to bias offspring sex ratios has traditionally been dismissed given the expectation of an equal proportion of X- and Y-chromosome-bearing sperm (CBS) in ejaculates due to segregation of sex chromosomes at meiosis. This expectation has been recently refuted. Here we used Peromyscus leucopus to demonstrate that sex ratio is explained by an exclusive effect of the father, and suggest a likely mechanism by which male-driven sex-ratio bias is attained. We identified a male sperm morphological marker that is associated with the mechanism leading to sex ratio bias; differences among males in the sperm nucleus area (a proxy for the sex chromosome that the sperm contains) explain 22% variation in litter sex ratio. We further show the role played by the sperm nucleus ar...
Page 1. Modelling survival and capture probabilities of the mountain brushtail possum (Trichosuru... more Page 1. Modelling survival and capture probabilities of the mountain brushtail possum (Trichosurus caninus) in the forests of south-eastern Australia using trap±recapture data DB Lindenmayer1*, RC Lacy2 and KL Viggers3 ...
Habitat loss and habitat fragmentation can have major effects on the distribution and abundance o... more Habitat loss and habitat fragmentation can have major effects on the distribution and abundance of species (Saunders et al. 1987), often in unpredictable ways (Klein 1989; Tilman et al. 1994; Lacy and Lindenmayer 1995; Cunningham and Moritz 1998). An understanding of responses of species, which lead to persistence or extinction in such disturbed systems, is important for the effective management of many taxa in fragmented multi-use landscapes. One way to examine population dynamics in fragmented systems is to analyse the genetic characteristics of subpopulations in remnant habitat patches (Sarre 1995), borrowing from the population genetics literature for the interpretation of key effects. For example, it is well established that a small, completely isolated population will lose genetic variation rapidly due to genetic drift (Lacy 1987). However, loss of genetic variation within, and increasing differentiation between, subpopulations will be counteracted by inter-population dispersa...
Animals with only partially known ancestry present a problem for population managers because it c... more Animals with only partially known ancestry present a problem for population managers because it can be difficult to determine their relative genetic value to the population. So long as their ancestry is not completely unknown, population management software such as PMx can calculate a mean kinship for these animals, but that mean kinship is calculated such that there is no decrease in relative genetic value or "penalty" for only partially known ancestry. However, there is a longer-term genetic cost to having animals with only partially known ancestry in the population, and thus it is appropriate to "penalize" animals with partially known ancestry to some extent. The challenge is determining the correct "penalty" which will serve to decrease the percent unknown ancestry in subsequent generations while not causing excessive selection against the known ancestry of the animal. A new parameter of relative genetic value is developed which takes into account b...
... Present address: Department of Biology, Franklin and Marshall College, Lancaster, Pennsylvani... more ... Present address: Department of Biology, Franklin and Marshall College, Lancaster, Pennsylvania 17604. ... unrelated conspecifics: In lab tests, the half sibs show more "passive body contact" and fewer interactions related to aggres-sion than do nonkin (Kareem and Barnard ...
Sex ratio allocation has important fitness consequences, and theory predicts that parents should ... more Sex ratio allocation has important fitness consequences, and theory predicts that parents should adjust offspring sex ratio in cases where the fitness returns of producing male and female offspring vary. The ability of fathers to bias offspring sex ratios has traditionally been dismissed given the expectation of an equal proportion of X- and Y-chromosome-bearing sperm (CBS) in ejaculates due to segregation of sex chromosomes at meiosis. This expectation has been recently refuted. Here we used Peromyscus leucopus to demonstrate that sex ratio is explained by an exclusive effect of the father, and suggest a likely mechanism by which male-driven sex-ratio bias is attained. We identified a male sperm morphological marker that is associated with the mechanism leading to sex ratio bias; differences among males in the sperm nucleus area (a proxy for the sex chromosome that the sperm contains) explain 22% variation in litter sex ratio. We further show the role played by the sperm nucleus ar...
Page 1. Modelling survival and capture probabilities of the mountain brushtail possum (Trichosuru... more Page 1. Modelling survival and capture probabilities of the mountain brushtail possum (Trichosurus caninus) in the forests of south-eastern Australia using trap±recapture data DB Lindenmayer1*, RC Lacy2 and KL Viggers3 ...
Habitat loss and habitat fragmentation can have major effects on the distribution and abundance o... more Habitat loss and habitat fragmentation can have major effects on the distribution and abundance of species (Saunders et al. 1987), often in unpredictable ways (Klein 1989; Tilman et al. 1994; Lacy and Lindenmayer 1995; Cunningham and Moritz 1998). An understanding of responses of species, which lead to persistence or extinction in such disturbed systems, is important for the effective management of many taxa in fragmented multi-use landscapes. One way to examine population dynamics in fragmented systems is to analyse the genetic characteristics of subpopulations in remnant habitat patches (Sarre 1995), borrowing from the population genetics literature for the interpretation of key effects. For example, it is well established that a small, completely isolated population will lose genetic variation rapidly due to genetic drift (Lacy 1987). However, loss of genetic variation within, and increasing differentiation between, subpopulations will be counteracted by inter-population dispersa...
Animals with only partially known ancestry present a problem for population managers because it c... more Animals with only partially known ancestry present a problem for population managers because it can be difficult to determine their relative genetic value to the population. So long as their ancestry is not completely unknown, population management software such as PMx can calculate a mean kinship for these animals, but that mean kinship is calculated such that there is no decrease in relative genetic value or "penalty" for only partially known ancestry. However, there is a longer-term genetic cost to having animals with only partially known ancestry in the population, and thus it is appropriate to "penalize" animals with partially known ancestry to some extent. The challenge is determining the correct "penalty" which will serve to decrease the percent unknown ancestry in subsequent generations while not causing excessive selection against the known ancestry of the animal. A new parameter of relative genetic value is developed which takes into account b...
... Present address: Department of Biology, Franklin and Marshall College, Lancaster, Pennsylvani... more ... Present address: Department of Biology, Franklin and Marshall College, Lancaster, Pennsylvania 17604. ... unrelated conspecifics: In lab tests, the half sibs show more "passive body contact" and fewer interactions related to aggres-sion than do nonkin (Kareem and Barnard ...
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