Abstract

Population structure is an important aspect of patchily distributed organisms. Small local populations, large temporal fluctuations, synchronized dynamics, and low migration rates should all lead to lowered rates of patch occupancy and increased extinction risks. These effects can, however, be counteracted if there is a pool of hidden, dormant individuals bridging unfavorable periods. Prolonged diapause-a dormancy that extends over two or more years-provides such a temporal bridge among insects, but its role in structuring patchy populations is poorly known. Based upon a long-term study, we explore the landscape scale population structure of a galling insect, the larva of which has an unusually long diapause spent hidden in the soil. Gall populations in patches fluctuated synchronously in a long wave with a tenfold amplitude. Abundances were very low with a median of less than twenty galls per patch. Although only a third of the patches had galls in all years, local populations persisted thanks to the pool of diapausing larvae. Colonizations of two new plant patches were very slow. The combination of small, synchronously fluctuating gall populations and high occupancy rates can be maintained because of the very low extinction rates imposed by the time-traveling diapausing larvae.

Keywords

gall midge; occupancy; patchy populations; population density; prolonged diapause; swallow-wort

Published in

Ecosphere
2020, volume: 11, number: 3, article number: e03086
Publisher: WILEY

Authors' information