For two tree variety into the Sri Lanka’s wet zone forests, fruit place increased significantly that have outcrossing length, peaking at intermediate-point within-tree crosses (1–10 km depending on types). During the crosses anywhere between woods occupying separate tree reserves, although not, fruit set is actually notably faster (otherwise almost so) both for kinds. However, seeds germination and you can seedling peak from the 1 year getting Sh. cordifolia ideal hybrid vigor in-between-tree crosses. The effects away from nearest-next-door neighbor mating ranged certainly trees and you will species; new indicate physical fitness price of nearby-next-door neighbor mating in line with mating which have moderately a great deal more faraway neighbors was 45% getting S. rubicundum and you will 0% getting Sh. cordifolia. Having said that, the newest physical fitness ramifications of between-forest crossing was generous for varieties (52 and you will 70% prior to contained in this-forest crosses for the same two varieties). Crossing consequences decreased between your levels off good fresh fruit set and step 1-yr-dated seedling dimensions; only the former is actually significant for both species. Overall performance imply a robust prospect of biparental inbreeding despair contained in this forest tree populations and you may partial reproductive separation certainly one of trees occupying the remaining forest supplies into the Sri Lanka’s wet area.
Inbreeding depression can often be cited just like the an unavoidable results of anthropogenic disturbance so you’re able to warm forests (age.g., forest fragmentation, logging), where concept predicts one typical mating designs inside currently lowest-density forest populations are moved on so you can favor small-point crosses. Up to now, not, the effects away from elevated close-next-door neighbor mating to have people physical fitness for the exotic woods have yet to help you feel quantified empirically. Several practical inquiries to-be handled try: Perform grownups stop maturing seeds produced from near-neighbors crosses and you may, if you don’t, how fit is actually close-neighbor-derived progeny according to anyone else? This study analyzes the consequences off close-neighbor mating in two tropical tree species physically as a result of physical fitness evaluations out-of crosses ranging from nearby natives which have crosses involving a whole lot more distant mates.
Shorea cordifolia (Dipterocarpaceae) is a locally numerous fundamental shelter varieties you to meilleur site de rencontre pour joueurs definitely plants heavily within abnormal supra-yearly durations (I. An excellent. U. N. Gunatilleke et al., unpublished study). Flowers of the variety try light and you will short-lived, in addition to winged fruit was distributed because of the breeze or the law of gravity. For its highly limited seed dispersal, hereditary relatedness certainly one of near neighbors inside absolute forest is expected so you’re able to be high. In the signed tree from the Sinharaja, Sh. cordifolia always occurs in clumps out-of ?5–20 adults, intermixed with quicker stems (personal observation).
Research research
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 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%, F1,58 = 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 one,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). 2,8 = 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 one,12 = 8.77, P = 0.012).
Near-neighbor crossing impression
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.