We discovered that the current mitochondrial DNA genetic make-up of the argentatus showed clear signs of past hybridisation between birds derived from different ancestral refugia, although no definite geographic scenario could be reconstructed for this reticulation because of insufficient sampling in our previous study.
To reject the null hypothesis of allopatric fragmentation, in which samples were grouped according to the geographic scenario described above, we should observe a significantly smaller s between the recovered gene tree and our hypotheses than between gene trees simulated under an allopatric fragmentation and our hypotheses.
Equine and swine influenza viruses, for example, both exhibit a strong separation of American and Eurasian strains [16], [38], and recombination events involving parents located on different continents should be treated with caution; the global trade in swine and poultry will make some geographic scenarios more plausible than others [39], [40].
Estimations of rates of radiation, as well as the reconstruction of past geographic scenarios of divergence, require the incorporation of a temporal axis into phylogenetic reconstructions [ 5- 7].
Moreover, spatial and temporal constraints (e.g., area distances, continent connections, dates of geological origin) may be imposed in the DEC model estimation, providing a more accurate estimation of the ancestral ranges and hypothesis testing of different geographic scenarios.
Although Stockwell and Peterson and Hernandez found that as few as 10 presence points are adequate for accurate GARP models [ 36, 39], additional work has shown that certain species or geographic scenarios are more sensitive to sample size than others and that model accuracy can be sensitive to both sample size and extent of the species' range [ 42].
In contrast, the structure scenarios based on geographic barriers (scenario 2) or based on an intercontinental migratory divide (scenario 3) revealed no significant among-group differences (Table 2).
The observed number of non-overlapping pairs was less useful in discriminating geographic speciation scenarios.
The study highlights that divergence processes are likely to be based on a variety of factors, and that little will be gained by exclusively adhering to a controversial debate about geographic speciation scenarios [ 7].
A key factor in the first scenario, geographic expansion, is the suitability of the landscape for the disease complex to become introduced and established.
SDMs are increasingly used to predict climatic suitability in novel geographic or temporal scenarios and require improvements in performance.
