For two tree species into the Sri Lanka’s damp zone forest, fruits set more than doubled with outcrossing range, peaking within advanced-length within this-tree crosses (1–10 km based kinds). Within the crosses between trees occupying separate forest reserves, however, fruits place are notably quicker (otherwise nearly so) for kinds. Conversely, seed germination and you can seedling peak during the step 1 yr for Sh. cordifolia recommended crossbreed vitality in the middle-forest crosses. The consequences from nearest-neighbor mating varied certainly trees and you may types; the brand new indicate fitness cost of nearby-neighbor mating prior to mating with moderately much more distant locals is actually 45% to possess S. rubicundum and you may 0% to own Sh. cordifolia. Conversely, the new exercise negative effects of between-forest crossing was reasonable for both variety (52 and you will 70% prior to inside-tree crosses for similar a couple species). Crossing effects decreased between your degrees of fruit lay and step 1-yr-old seedling size; only the former try extreme for kinds. Performance imply an effective potential for biparental inbreeding depression within tree tree communities and you can limited reproductive separation one of woods consuming the remainder tree supplies within the Sri Lanka’s damp region.
Inbreeding despair is commonly cited due to the fact an inevitable result of anthropogenic interference in order to warm woods (elizabeth.grams., tree fragmentation, logging), where principle forecasts that regular mating habits contained in this currently reduced-density tree communities is actually shifted in order to favor short-point crosses. Up to now, although not, the effects off increased near-neighbors mating having populace fitness for the warm woods provides but really so you’re able to end up being quantified empirically. Several standard concerns is addressed try: Carry out people avoid maturing seed produced from near-neighbor crosses and you may, if you don’t, exactly how complement was close-neighbor-derived progeny in line with someone else? This research assesses the effects of close-neighbors mating in two exotic tree species directly as a consequence of physical fitness contrasting away from crosses ranging from nearest locals having crosses of so much more distant mates.
Shorea cordifolia (Dipterocarpaceae) was an in your area plentiful head cover varieties you to vegetation greatly on unusual supra-annual times (I. A beneficial. U. Letter. Gunatilleke mais aussi al., unpublished research). Vegetation of this variety try white and you may brief-stayed, therefore the winged good fresh fruit try distribute from the snap or gravity. Because of its extremely minimal seed dispersal, genetic relatedness one of near residents during the sheer forest is anticipated so you’re able to be large. From inside the signed forest on Sinharaja, Sh. cordifolia always occurs in clumps of ?5–20 adults, intermixed that have reduced stems (individual observation).
Study study
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 sites de rencontres pour adultes de 30 ans.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). 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,twelve = 8.77, P = 0.012).
Near-neighbors crossing perception
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.
