Study Shows Birds Disperse Eaten Insects' Eggs

Arthur T Knackerbracket has processed the following story:

Relationship patterns among flightless stick insects suggest that birds disperse the eggs after eating gravid females. Lab experiments previously suggested the possibility, but a new genetic analysis of natural populations in Japan by Kobe University researchers now supports the idea.

Most species of stick insects are flightless, yet they are distributed over wide distances and across geographical features that would impede the expansion of flightless animals. This has caused researchers to speculate that their eggs might be dispersed by birds feeding on gravid females, much in the same way as many plant species rely on birds eating their seeds together with fruits and dispersing them while the seeds pass through the digestive tracts of the birds unharmed.

Experimental studies with Ramulus mikado, a common stick insect in Japan, had suggested that this is possible, but since direct observation of such an event in nature is highly unlikely, it has been unclear whether this mechanism actually contributes to the distribution of the insect.

[...] Lead author Suetsugu says, "Astonishingly, amidst a sea of limited active dispersal, we discovered identical genotypes jumping across vast distances, strongly indicating the past occurrence of passive long-distance genetic dispersal." In other words, a few of the flightless insects must have flown from place to place, and the only plausible way in which this could happen is that the eggs of the insects survive the passage through the digestive tract of birds that eat them.

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