Rising temperature are threatening many frog species , and place a particular challenge for burrowing frogs , which survive long dry periods in arid zone by burying themselves and wait for pelting . However , three Australian species seem to be coping amazingly well and they have one feature in vernacular – four sets of chromosomes instead of the common two .
A oversupply of chromosomes , known aspolyploidy , is rough-cut in plants , but rare in animals , specially vertebrates . Polyploidy sometimes happens when animate being hybridize , Dr Ian Brennanof the Australian National University told IFLScience , with offspring somehow ending up with both sets of chromosomes from each parent . Unusual conditions , such as exposure to certain chemical or freezing cycles , can induce what is known asautopolyploidy , where a doubling up occurs without hybridization . Even more exotic events can allow for an organism with three or six sets of chromosomes .
Extra chromosome usually interfere with breeding , however , so polyploid animal commonly regurgitate asexually , pull in the Australian genusNeobatrachusan exception among exceptions . There are nine known species ofNeobatrachusfrogs , six diploid ( the common two chromosome exercise set ) , while three are tetraploid ( four chromosome sets ) . All are intimate .
Brennan is part of a team that describe theNeobatrachusfamily tree diagram , particularly its tetraploid mintage inPLOS Genetics . Astonishingly , Brennan and co - authors report that the tetraploid species do not all descend from a single issue . They ’re sufficiently evolutionarily distant from each other , with diploid specie in - between , and they must have adopt the extra chromosome severally .
" It does n’t happen often – but here it ’s take place three times in one genus . And we ’re talking about three autonomous events , ” Brennan said in astatement . As to why this one genus is so prone to something almost unheard of elsewhere , Brennan could only tell IFLScience “ we have some ideas , but are not really positive . ”
Four chromosome sure as shooting mess up with the rife / recessionary Mendelian genetics we learned at school day , and Brennan told IFLScience agreement of what occur instead is still hazy . “ Sometimes only two copy are used to square off genetic influence , while the others just accumulate mutations , ” he add together .
For all its drawbacks , polyploidy seems to work for these salientian , and indeed the generator found it is the tetraploid species that are conform good as rainstorms become rarer and the heat between more intense .
" We thinkNeobatrachusdiploids might be suffering the early impacts of mood - induced habitat red ink , while the polyploid species seem to be avoiding this lot , " Brennansaid .
The author mean this is because the tetraploid species have greater genetic diversity . A lot of crossbreeding happen between the species , such that their category tree lacks a full-strength separate structure , more closely resemble a rosaceous bush . fresh gene get engage into tetraploid populations more easily than diploid 1 , offer more flexibility when conditions exchange .
