AboutZoos, Since 2008


First evi­dence of plants evolv­ing weaponry to com­pete in the strug­gle for selection

pub­lished 20 March 2014 | mod­i­fied 20 March 2014

Rut­ting stags and claw­ing bears are but two exam­ples of male ani­mals fight­ing over a mate, but research in New Phy­tol­o­gist has uncov­ered the first evi­dence of sim­i­lar male strug­gles lead­ing to the evo­lu­tion of weaponry in plants.

South American milkweedThe team, led by Dr. Andrea Cocucci from the Insti­tuto Mul­ti­dis­ci­pli­nario de Biolo­gia Veg­e­tal of Argentina, stud­ied a species of milk­weed (Apoc­y­naceae), found in trop­i­cal cli­mates. While plants do not mate like ani­mals, but rather repro­duce via pol­li­na­tors such as insects or birds, com­pe­ti­tion between indi­vid­u­als to exploit those pol­li­na­tors can result in con­fronta­tion between the plants.

Milk­weed repro­duce by hook­ing sacs of pollen grains, known as pollinia, to the bod­ies of birds and other pol­li­na­tors, which can be unwit­tingly dropped into another flower to com­plete pol­li­na­tion. It is pos­si­ble for mul­ti­ple pollinia sacs to become entan­gled together due to the lim­ited num­ber of attach­ment points on the pol­li­na­tor, and this Dr. Cocucci’s team believe, is the source of confrontation.

The team stud­ied the South Amer­ica milk­weed genus Oxypetalum and found horn-​like struc­tures on the pollinia sacs which have no obvi­ous bio­log­i­cal use. The paper sug­gests that these horns are used to pre­vent the sacs from being hooked together with pollinia from other par­ent plants.

Our results sug­gest that nei­ther self-​propulsion nor well-​developed sen­sory per­cep­tion are required for sex­ual selec­tion to take place through intra­sex­ual strug­gles. Appar­ently, only phys­i­cal con­tact is enough to influ­ence the mat­ing suc­cess of competitors and to pro­mote the evo­lu­tion of defen­sive and attack weaponry.
(Dr. Andrea Cocucci, Insti­tuto Mul­ti­dis­ci­pli­nario de Biolo­gia Veg­e­tal, Argentina)

(Source: Wiley press release, 20.03.2014)

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