Mating systems and reproductive success inferred via PBT
Results from parentage-based tagging identified a total of 934 unique
parent-pairs from a combinations of 373 male and 486 female Yellowstone
Cutthroat trout. The number of mates per adult was right skewed, with no
offspring contributions detected from 37.9% of females and 48.9%
(Figure 2A ). Of the adults that were assigned at least one
offspring, the most common number of mates per adult was one for both
females (27.7%) and males (24.2%). Individual females mated with up to
five different males, whereas males mated with up to 16 different
females (Figure 2A ). The mean number of mates was 1.19 (SD:
1.25) for females and 1.28 (SD: 2.02) for males. The median number of
mates was one for both males and females. Based on the reproductive
profiles of individual adults we identified evidence of monogamy,
polygyny, and polyandry.
Similar to the number of mates per adult, the distribution of relative
reproductive success was right skewed. Among adults that contributed to
reproduction, the most frequent number of offspring produced was one for
both females (13.3%) and males (11.9%; Figure 2B ). The
maximum number of offspring attributed to a female was 22, whereas one
male produced 57 offspring. The mean number of offspring produced per
female was 2.95 (SD: 3.89) and 3.16 (SD: 6.22) for males.
A positive relationship was identified between the number of mates and
the relative number of offspring produced (Figure 2C ). For both
females and males, the average number of offspring per adult increased
as a function of the number of mates acquired but the strength of this
correlation differed by sex. Specifically, Pearson’s correlation
coefficient between the number of offspring produced and number of mates
acquired was 0.77 and 0.89 for females and males, respectively.
The same set of 3,862 full-sibling pairs were identified by both sibship
assignment and parentage analysis. Seventeen full-sib pairs were
detected by sibship assignment only, and 35 full-sib pairs were detected
exclusively by parentage analysis. Discordance between methods (52 pairs
differed of 3,914 total pairs) was 1.3% indicating that both methods
produced highly similar results. Both analyses identified 410 offspring
that were ‘only children’ (i.e., had no full siblings) and an additional
33 ‘only children’ were detected by sibship assignment and not PBT.
Three ‘only children’ were detected by PBT but not sibship analysis.