Fifteen years of variability in relative density for Nysius wekiuicola, an endemic seed bug of conservation concern on the summit of the Maunakea volcano, Hawai‘i

The Hawaiian endemic wēkiu bug, Nysius wekiuicola, is a unique flightless insect that inhabits the rock tephra cinder cones above ~3,500 m elevation on the summit of the Maunakea volcano.  The wēkiu bug is a species of conservation concern due to: a) its restricted range of ~1,618 ha in alpine stone desert habitat and b) variability in observed relative densities.  This carnivorous scavenger species has evolved behavioral and morphological adaptations to withstand the harsh alpine environment at the mountain summit.  Although the wēkiu bug has been monitored annually since 2001 and intermittently since 1982, little is known about the insect’s densities and distributions through time.  Both direct habitat modification threats and indirect climate change or competitive species threats are not well understood.  We compiled all available wēkiu bug data to show intra- and inter-annual patterns, trends, and variability. 

Wēkiu bug capture rates and distribution patterns within and between cinder cones are extremely variable from year to year.  The greatest difference in wēkiu bug relative density was observed between the summers of 2013 and 2014 when capture abundances decreased from 5,290 to 52, at daily capture rates of 18.2 and 0.2 following a year of intense drought.  This decrease also corresponded to decreases in observed distributions within a cinder cone, where insects were absent from many of the monitoring sites.  Understanding the temporal variability and spatial distribution of this insect, in conjunction with abiotic data, can provide insights to land managers for the continued management and conservation of this species.