For two forest types inside Sri Lanka’s wet area woods, fresh fruit place increased significantly which have outcrossing distance, peaking during the advanced-point within this-tree crosses (1–10 kilometer dependent on types). Within the crosses between woods occupying independent tree supplies, although not, fresh fruit place is notably smaller (otherwise almost very) for types. However, seed germination and you will seedling top at 1 year having Sh. cordifolia suggested crossbreed vitality between-tree crosses. The results off nearby-neighbor mating ranged among trees and you will variety; the latest mean fitness price of nearest-neighbors mating in accordance with mating that have modestly alot more faraway natives is actually 45% to possess S. rubicundum and you can 0% to possess Sh. cordifolia. Conversely, the fitness outcomes of ranging from-tree crossing had been big for kinds (52 and you can 70% prior to within-tree crosses for the very same a couple varieties). Crossing effects diminished between your grade out-of fruits place and you may step 1-yr-old seedling dimensions; just the previous is significant both for kinds. Results indicate a strong possibility biparental inbreeding depression within forest tree populations and you may partial reproductive separation among trees consuming the rest tree supplies during the Sri Lanka’s moist area.
Inbreeding anxiety can be quoted given that an unavoidable consequence of anthropogenic disturbance in order to warm forest (age.grams., forest fragmentation, logging), in which theory forecasts you to definitely regular mating models within this already reasonable-occurrence tree communities try managed to move on to help you choose small-distance crosses. At this point, but not, the consequences off raised near-neighbor mating to possess population fitness inside tropical trees enjoys but really so you’re able to end up being quantified empirically. One or two basic issues is treated is actually: Manage adults end maturing seeds produced by close-next-door neighbor crosses and you can, if not, how fit is close-neighbor-derived progeny in line with other people? This research assesses the effects out-of close-neighbor mating in two exotic forest kinds really owing to fitness contrasting off crosses anywhere between nearby neighbors with crosses of even more distant friends.
Shorea cordifolia (Dipterocarpaceae) is actually a locally plentiful chief canopy varieties one to plant life greatly on unusual supra-annual intervals (I. Good. You. N. Gunatilleke mais aussi al., unpublished studies). Plant life of varieties are white and you can quick-stayed, and the winged fresh fruit are distribute of the snap otherwise the law of gravity. For the very minimal seed products dispersal, genetic relatedness certainly one of close residents in natural forest is expected in order to feel high. During the signed forest during the Sinharaja, Sh. cordifolia usually takes place in clumps of ?5–20 adults, intermixed having faster stems (individual observation).
For both species, within-treatment variation among maternal trees in fruit set was substantial for all outcrosses involving pollen donors within Sinharaja Reserve. In contrast, variation in fruit set rate was very low for between-forest crosses (Fig. 2). For Sh. cordifolia, fruit set for sites de rencontre pour cÃ©libataires espagnols the distant between-forest treatment ranged from only 0.5 to 0.6% and was significantly lower than the mean fruit set rate for all within-forest outcrossing treatments combined (mean = 2.71%, Fstep 1,58 = 9.94, P < 0.0003). For S. rubicundum, mean fruit set for the distant between-forest treatment (2.67%) was low relative to mean fruit set rate for all within-forest outcrossing treatments combined (mean = 5.97%). The difference was nearly significant (Fstep 1,58 = 3.78, P < 0.06).
For Sh. cordifolia, cumulative fitness was maximum at both the distant neighbor and distant within-forest treatments (Fig. 5). Peak cumulative fitness observed for these intermediate crossing treatments was 2 and 4.3 times the cumulative fitnesses of the nearest-neighbor and distant between-forest treatments, respectively, although these differences were not significant (Table 3B). dos,8 = 3.70, P = 0.073). Mean cumulative fitness of open-pollinated flowers exceeded that of all other hand-pollination treatments, again likely due to the detrimental effect of the hand-pollination procedure on fruit set in this species. As for fruit set, mean cumulative fitness (relative) of the distant between-forest treatment (mean = 0.12) was significantly lower than that of all within-forest outcrossed classes combined (mean = 0.51, Fstep 1,12 = 8.77, P = 0.012).
Near-neighbor crossing effects have been demonstrated for a number of coniferous species (Coles and Fowler, 1976; Park and Fowler, 1982, 1984; Latta et al., 1998), but only three studies have yielded evidence of near-neighbor crossing effects in woody angiosperms (Syzygium cormiflorum-Crome and Irvine, 1986; Schiedea spp.-Sakai, Karoly, and Weller, 1989; Eucalyptus globules-Hardner, Potts, and Gore, 1998). In another study suggestive of biparental inbreeding depression, mean fruit set rates were significantly lower for intraspecific crosses <0.5 km distance than for crosses >1 km distance for three subcanopy tree species (Inga spp.) in Costa Rica (Koptur, 1984). In fact, it may be that biparental inbreeding depression is common in natural populations of forest trees, but that estimation of its potential through experimental cross-pollinations has been limited to only a few species due to the obvious difficulty of working in the canopy. To my knowledge, there are no published reports of failed attempts to find near-neighbor crossing effects in natural populations of forest trees.