Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!husc6!seismo!mcnc!duke!evs From: evs@duke.UUCP Newsgroups: sci.bio Subject: Re: Synchronized flowering Message-ID: <9336@duke.duke.UUCP> Date: Thu, 12-Mar-87 11:51:11 EST Article-I.D.: duke.9336 Posted: Thu Mar 12 11:51:11 1987 Date-Received: Fri, 13-Mar-87 21:51:54 EST References: <534@bcsaic.UUCP> Reply-To: evs@duke.UUCP (Ed Simpson) Organization: Duke University Medical Center, Durham, NC Lines: 45 In article <534@bcsaic.UUCP> michaelm@bcsaic.UUCP (Michael Maxwell) writes: >There is a fruit tree around here (Seattle) that has just put out beautiful >pink-purple flowers. What surprised >me is that all of the trees within the local area (several miles, at least) >seemed to flower within a day or so. I can see what an advantage this would >be for cross-pollenization, but how do they synchronize their flowering? >I suspect that it was a sudden warm day we just had after a cold spell. If >so, I would imagine that there is enough variability in the threshold of >individual trees that some years they're "fooled." That is, there >is a day which is enough warmer than previous days that some--but not >all--trees of this species flower. Has this been studied? If the Seattle population of trees was "ideal", then all trees in Seattle would always bloom at the same time. If, however, some of them then some tress will bloom and others won't. If they are using temperature as a cue then it is not hard to imagine that each tree has some internal temperature threshold that is genetically controlled. Then assuming that proximal trees are closely related, we would expect trees to bloom in pockets (local areas, as Michael observed). What this effectively does is to create locally isolated popluations, thus increasing the inbreeding in the Seattle metapopulation. This inbreeding would tend to make proximal trees in future generations even more closely related, thus possibly accentuating the pocket blooming effect the next time we get an isolated warm day. So in years when we get short warm periods that "fool" only some of the population, inbreeding should increase. But then some years we may not get a warm day until spring has come for real. Then all trees would bloom more or less at the same time and inbreeding should decrease. Thus it may be that the inbreeding coefficient (measure of inbreeding for a population) for the Seattle population is fluctuating over time. However if false springs and true springs alternate years or something close to that, the inbreeding coefficient may just be an average of these yearly fluctuations. L.L. Cavalli-Sforza has looked at inbreeding and genetic drift in isolated human populations in the Parma River valley in Italy. He used blood groups in his study. See: Cavalli-Sforza, L.L., and W.F. Bodmer. 1971. "The Genetics of Human Populations." San Francisco: Freeman. -- UUCP: {decvax, seismo}!mcnc!duke!evs ARPA: evs@cs.duke.edu CSNET: evs@duke Ed Simpson, P.O.Box 3140, Duke Univ. Medical Center, Durham, NC, USA 27710