scholarly journals The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos

2016 ◽  
Vol 12 (12) ◽  
pp. 20160693 ◽  
Author(s):  
P. Morán ◽  
L. Labbé ◽  
C. Garcia de Leaniz
Keyword(s):  
Sex Determination ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Marker ◽  
Brown Trout ◽  
Sex Ratios ◽  
High Survival ◽  
Effective Population ◽  
Genetic Incompatibility ◽  
Bias Selection

Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates.

Spatial and temporal genetic differentiation and effective population size of brown trout (Salmo trutta, L.) in small Danish rivers

2005 ◽  
Vol 6 (4) ◽  
pp. 615-621 ◽  
Author(s):  
Lasse F. Jensen ◽  
Michael M. Hansen ◽  
Jens Carlsson ◽  
Volker Loeschcke ◽  
Karen-Lise D. Mensberg
Keyword(s):  
Genetic Differentiation ◽  
Population Size ◽  
Effective Population Size ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Effective Population ◽  
Brown Trout Salmo Trutta

scholarly journals Consequences of sex change for effective population size

2018 ◽  
Vol 285 (1893) ◽  
pp. 20181702 ◽  
Author(s):  
Robin S. Waples ◽  
Stefano Mariani ◽  
Chiara Benvenuto
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Evolutionarily Stable Strategy ◽  
Sex Ratios ◽  
Sex Change ◽  
Standard Theory ◽  
Effective Population ◽  
Potential Conflict ◽  
Individual Level ◽  
The Individual

Sequential hermaphroditism, where males change to females (protandry) or the reverse (protogyny), is widespread in animals and plants, and can be an evolutionarily stable strategy (ESS) if fecundity rises faster with age in the second sex. Sequential hermaphrodites also generally have sex ratios skewed towards the initial sex, and standard theory based on fixed sexes indicates that this should reduce effective population size ( N e ) and increase the deleterious effects of genetic drift. We show that despite having skewed sex ratios, populations that change sex at the ESS age do not have reduced N e compared with fixed-sex populations with an even sex ratio. This implies that the ability of individuals to operate as both male and female allows the population to avoid some evolutionary constraints imposed by fixed sexes. Furthermore, N e would be maximized if sex change occurred at a different (generally earlier) age than is selected for at the individual level, which suggests a potential conflict between individual and group selection. We also develop a novel method to quantify the strength of selection for sex reversal.

scholarly journals Long-term monitoring of a brown trout (Salmo trutta) population reveals kin-associated migration patterns and contributions by resident trout to the anadromous run

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Eloïse Duval ◽  
Øystein Skaala ◽  
María Quintela ◽  
Geir Dahle ◽  
Aurélien Delaval ◽  
...  
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Anthropogenic Pressure ◽  
Parentage Assignment ◽  
Effective Population ◽  
Migration Timing ◽  
Brown Trout Salmo Trutta ◽  
And Migration

Abstract Background In species showing partial migration, as is the case for many salmonid fishes, it is important to assess how anthropogenic pressure experienced by migrating individuals affects the total population. We focused on brown trout (Salmo trutta) from the Guddal River in the Norwegian Hardanger Fjord system, which encompasses both resident and anadromous individuals. Aquaculture has led to increased anthropogenic pressure on brown trout during the marine phase in this region. Fish traps in the Guddal River allow for sampling all ascending anadromous spawners and descending smolts. We analyzed microsatellite DNA markers from all individuals ascending in 2006–2016, along with all emigrating smolts in 2017. We investigated (1) if there was evidence for declines in census numbers and effective population size during that period, (2) if there was association between kinship and migration timing in smolts and anadromous adults, and (3) to what extent resident trout were parents of outmigrating smolts. Results Census counts of anadromous spawners showed no evidence for a decline from 2006 to 2016, but were lower than in 2000–2005. Estimates of effective population size also showed no trends of declines during the study period. Sibship reconstruction of the 2017 smolt run showed significant association between kinship and migration timing, and a similar association was indicated in anadromous spawners. Parentage assignment of 2017 smolts with ascending anadromous trout as candidate parents, and assuming that unknown parents represented resident trout, showed that 70% of smolts had at least one resident parent and 24% had two resident parents. Conclusions The results bear evidence of a population that after an initial decline has stabilized at a lower number of anadromous spawners. The significant association between kinship and migration timing in smolts suggests that specific episodes of elevated mortality in the sea could disproportionally affect some families and reduce overall effective population size. Finally, the results based on parentage assignment demonstrate a strong buffering effect of resident trout in case of elevated marine mortality affecting anadromous trout, but also highlight that increased mortality of anadromous trout, most of which are females, may lower overall production in the system.

Sign in / Sign up

Export Citation Format

Share Document