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How has communication behavior developed over evolutionary time?
How has communication behavior developed over evolutionary time?
Class: Mammalia Order: Rodentia Family: Castoridae Genus and Species: Castor canadensis
Class: Mammalia Order: Rodentia Family: Castoridae Genus and Species: Castor canadensis
Background
Background
Beavers are in the rodent order and in the genus Castoridae which only have two living species in it today, Castor fiber and Castor canadensis. They are more commonly known as the American beaver and the Eurasian beaver named after their ranges. They do not have many morphological differences; however, their molecular make ups differentiate them. They are the second largest rodents and are distinguished by their large flat tails, aquatic abilities, and castor glands. They are very ecologically distinct among the rodent species. There is little known about their evolution and phylogenetic relationships, so all these conclusions are hypothesis (Horn et al, 2011).
Ancestry
Ancestry
Beavers date back to 40 million years ago which puts the emergence of the genus Castor to have appeared in the late Miocene and Pliocene era. The genus Cator is a close relative to steneofiber and could have dispersed to north America through the land bridge about 6 million years ago. It is unclear how then the two species of Castor emerged from there. It could have been caused by this dispersion across the Bering strait. Cator is categorized in the mouse related clade of rodents and puts it as a sister group to the Anomalurus which is a scaly tailed squirrel. This diversion between these two groups happened around 54 million years ago. All rodents are through to have shared a common ancestor around 67 million years ago, although this common ancestor is unknown (Doronia, 2017).
This phylogenetic tree shows the time scale of the speciation events between clades and species. Within the rodents, there is the mouse-related clade, hystricofnathi, and the squirrel-related clade. There are also many outgroups. Beavers are correlated with the mouse-related clade. This phylogenetic tree also shows the time periods that all of these divergent events occurred. It shows that there is a common ancestor to the beavers called Anomaluromorpha around 54 million years ago. Then the two beaver species diverged around 8-7.6 million years ago. The numbers on the branches are the bootstrap values that are the degree of confidence to the position of the branches (Doronina, 2017).
This phylogenetic relationship is based on the zygomatic structure of the skulls of the different rodents. The lateral masseter is shifted anterodorsally and originates on the rostrum in the sciuromorphs. This puts the beaver in close relationship with the kangaroo mouse and the scaly-tailed squirrel (Horn et al., 2011).
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