VARIABILITY IN TEMPERATURE AND HISTORICAL PATTERNS IN REPRODUCTION IN THE FUCUS DISTICHUS COMPLEX (HETEROKONTOPHYTA; PHAEOPHYCEAE): IMPLICATIONS FOR SPECIATION AND THE COLLECTION OF HERBARIUM SPECIMENS1

Abstract

Natural and anthropogenic‐induced fluctuations in temperature can have profound effects on an organism's reproduction. The potential of herbarium collections for detecting changes in the timing of reproduction associated with interannual fluctuations in temperature from 1905 to 2003 was assessed in several taxa in the Fucus distichus (L.) emend. Powell complex from northern New England. Data were also used to evaluate whether air and/or sea temperature and North Atlantic Oscillation indices can cause overlap in the reproductive seasonalities of these taxa, a potential mechanism that prevents speciation. For all taxa, there was much variability in reproductive seasonalities among years. Discerning potential correlations with air or sea temperature was difficult because of a suspected bias to collect reproductive specimens at times when most of the population was nonreproductive. Nevertheless, there was a trend for seawater temperature to explain aseasonal reproduction for some taxa. Moreover, the existing archive (1895–2003) shows that the reproductive seasons of these taxa often overlap, and we suggest that interannual variability in temperature may often inhibit speciation. Suggestions also include archive of both reproductive and vegetative materials as well as coordinated sampling in critical biogeographic regions. No one investigator or institution can accomplish this, but phycological societies could organize and sustain such efforts.