Media Releases

University of Toronto biologists identify influence of environment on sexual vs. asexual reproduction

October 14, 2010

TORONTO, ON – Evo­lu­tion­ary biol­o­gists at the Uni­ver­si­ty of Toron­to (U of T) have found that envi­ron­ment plays a key role in deter­min­ing whether a species opts for sex­u­al over asex­u­al repro­duc­tion.

The study, led by post-doc­tor­al stu­dent Lutz Becks and Pro­fes­sor Aneil Agraw­al of the Depart­ment of Ecol­o­gy & Evo­lu­tion­ary Biol­o­gy, found that species that inhab­it spa­tial­ly het­eroge­nous envi­ron­ments – habi­tats char­ac­ter­ized by uneven con­cen­tra­tions of its own species among a rich vari­ety of oth­er ani­mals and plants – had high­er rates of sex­u­al repro­duc­tion than those in more homoge­nous envi­ron­ments.

“Sex­u­al repro­duc­tion is per­va­sive across the tree of life,” says Agraw­al. “One of the clas­sic ques­tions in evo­lu­tion­ary biol­o­gy is to deter­mine why most organ­isms repro­duce sex­u­al­ly rather than asex­u­al­ly. What­ev­er evo­lu­tion­ary force main­tains this mode of repro­duc­tion across such a diver­si­ty of life must be one of the most pow­er­ful and impor­tant fac­tors in biol­o­gy.  Our work sug­gests that spa­tial het­ero­gene­ity is one of these key fac­tors.”

Fur­ther­more, sex­u­al repro­duc­tion result­ed in organ­isms that are adept across dif­fer­ent envi­ron­ments, with dif­fer­ent char­ac­ter­is­tics and more robust genet­ic con­sti­tu­tions than their asex­u­al­ly-repro­duc­ing coun­ter­parts.

“Put sim­ply, sex­u­al repro­duc­tion helps cre­ate geno­types that are bet­ter able to sur­vive across dif­fer­ent envi­ron­ments.  In con­trast, asex­u­al repro­duc­tion yields types that are suit­ed to only one envi­ron­ment,” says Agraw­al.

The sci­en­tists con­duct­ed their exper­i­ments with rotifers – small aquat­ic organ­isms that are capa­ble of both sex­u­al and asex­u­al repro­duc­tion.  They allowed pop­u­la­tions of rotifers to evolve in habi­tats that were either envi­ron­men­tal­ly homo­ge­neous or het­ero­ge­neous.  Over a span of more than 70 gen­er­a­tions, the ten­den­cy for sex­u­al repro­duc­tion per­sist­ed at much high­er lev­els in het­ero­ge­neous habi­tats and declined rapid­ly in homo­ge­neous envi­ron­ments

The find­ings appear in the paper “High­er rates of sex evolve in spa­tial­ly het­ero­ge­neous envi­ron­ments” pub­lished Octo­ber 13 in Nature.  The research is sup­port­ed by fund­ing from the Nat­ur­al Sci­ences and Engi­neer­ing Research Coun­cil of Cana­da and a fel­low­ship from the Volk­swa­gen Foun­da­tion in Ger­many award­ed to Becks.

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For more infor­ma­tion, please con­tact:

Aneil Agraw­al
Depart­ment of Ecol­o­gy and Evo­lu­tion­ary Biol­o­gy
Uni­ver­si­ty of Toron­to

Sean Bet­tam
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to

Chris­tine Elias
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to