Crosses between members of generally separated communities, ergo, could possibly get give progeny out-of suboptimal physical fitness because of outbreeding despair (Bateson, 1978; Price and you will Waser, 1979). Most evidence of outbreeding depression in flowers comes away from crosses anywhere between communities (age.g., Ritland and you may Ganders, 1987; Sobrevila, 1988; Fischer and you may Matthies, 1997). But not, proof of outbreeding despair contained in this communities has been stated for good couples species (Waser and you will Rates, 1983, 1989, 1991, 1993, 1994; Schemske and you can Pautler, 1984; Waser mais aussi al., 1987; McCall, Mitchell-Olds, and you can Waller, 1988). Ultimate outcomes out of outbreeding anxiety ought to include support of reproductive isolation by the range and you can improved genetic differentiation over particular spatial measure, maybe causing speciation. Inside tropical forest, models with the evolution out of high tree varieties variety generally invoke genetic divergence out-of populations over some spatial measure (age.grams., Fedorov, 1966; Ashton, 1969). Very little is well known, although not, of spatial level regarding genetic divergence when you look at the tropical forest kinds.
If you’re style into outbreeding depression was indeed reported to possess lots of plant kinds (citations more than), there are no blogged account off outbreeding depression in almost any tree tree (Coles and you can Fowler, 1976; Playground and you can Fowler, 1982, 1984; Crome and you can Irvine, 1986; Hardner, Potts, and Gore, 1998). This research assesses the value and approximate spatial scale out-of outbreeding despair (since an excellent proxy getting hereditary divergence) in 2 tropical forest types compliment of fitness evaluations of enough time-distance crosses that have crosses over short and you will modest distances.
For every single of two tropical tree varieties, the second issues was in fact addressed: (1) How does get across-virility are very different with outcrossing length? (2) What’s the possibility inbreeding depression when you look at the close-next-door neighbor crosses? (3) What is the possibility of outbreeding anxiety more higher ranges within and you may ranging from tree reserves? and (4) Just how can brand new characteristics off inbreeding and you will outbreeding outcomes will vary one of very early life background amounts, plus seed products place, vegetables germination, plus the survivorship and you can growth of seedlings?
Studies website and species
This work are carried out in the room of aseasonal Sinharaja Globe Heritage Web site, a keen 8800-ha, UNESCO Boy therefore the Biosphere Reserve, found in the southwestern damp region off Sri Lanka (Fig. 1). The newest forests away from southwest Sri Lanka is actually seriously fragmented once the a beneficial result of cleaning for coffee-and rubber ranches that happened inside the United kingdom colonial period (>one hundred yr in the past)pared to many tropical precipitation forest, the fresh flowers out of Sinharaja is relatively types-terrible (?230 species of woody vegetation), but described as highest endemism (Gunatilleke and you can Gunatilleke, 1980). The research kinds (Syzygium rubicundum and you can Shorea cordifolia) was indeed picked to show a couple of biggest shelter-prominent, financially essential genera of island’s rain forest. Each other types is pollinated mostly of the bees (Apis spp.) and produce solitary-seeded good fresh fruit. The 2 species disagree during the function out-of seed products dispersal (bird- otherwise bat-dispersal versus. wind- or gyration-dispersal) and are expected to exhibit additional populace hereditary formations for the sheer really stands (Loveless and you will Hamrick, 1984; Hamrick, Murawski, and you may Nason, 1993). The newest communities targeted for this investigation, yet not, took place twenty five+-yr-dated logged forest from the Sinharaja Set aside. People of each and every types is actually very clumped on signed tree according to the distributions in unlogged really stands. That it compare means that the populace structures of them types provides started changed in the highest-light, post-signing ecosystem, in which regeneration more than likely resulted in the fresh business from sets of sibs if not associated somebody. The analysis populations, for this reason, provided a great possibility to evaluate the possibility biparental inbreeding despair during the forest woods.
Content And techniques
Syzygium rubicundum (Myrtaceae), and this generally speaking herbs a year, are a dominating shelter species of mid-slope section close by Sinharaja. Adult density is rencontre nudiste connexion highly varying both in unlogged and you may signed tree inside Sinharaja Set aside (Stacy, Harischandran, and Gunatilleke, when you look at the force). Herbs associated with kinds is small and clean-such as, and the drupes are mainly bird-distributed.