These approaches are generic, and may be incorporated into more complicated models that include multiple levels of nested variation (subpopulation, individual) or non-nested factors (sex, size class).
He suspects that our actions may account for much of the remaining nesting variation.
While most loggerhead nesting variation appears to be natural, Van Houtan insists that humans bear a good share of the blame.
The large variation in population estimates due to many forms of stochasticity (e.g. seasonal differences in decay rate, sampling bias and inter-nest variation in decay rate) appear to make it difficult to detect even large changes in population size.
Strong inter-nest variation in aromatic plant species composition is frequently observed, but there are few quantitative data, and most arguments so far come from qualitative field observations (e.g. [23]).
There was relatively little between-nest variation in the amount and quality of incubation (Tables 1– 3), but pairs varied considerably in their timing of incubation.
In support of this rule, we found striking synchronization between partners; exchanges between incubating birds were usually instantaneous (81% of exchange gaps were shorter than 1min), despite large within-nest variation in incubation bout length (nearly 2h).
The increase was consistent across nests (between-nest variation in the change of bout length over the incubation period accounted for less than 1.1% of the variance) but independent of the start of incubation within the season and independent of sex.
Given our findings, we suggest that nested variation, especially in the form of ecological sexual dimorphism, should be considered in greater detail for cases of adaptive divergence.
If trajectories match, then this could lend new weight to the idea that nested variation contributes to larger patterns of divergence.
Notably, this repeated pattern of divergence occurs despite differences in the age of the radiation or magnitude of morphological change, which is consistent with the idea that nested variation has accumulated to a greater or lesser extent in radiations of different ages.
