The connection between outcrossing length and you may cumulative fitness wasn’t significant (quadratic regression: F

For a couple of forest varieties in Sri Lanka’s moist zone forest, fresh fruit set more than doubled that have outcrossing range, peaking at intermediate-length within this-forest crosses (1–10 kilometer based species). Inside the crosses ranging from woods occupying separate tree reserves, but not, fruit put is significantly shorter (or almost therefore) for both kinds. Conversely, seed products germination and you may seedling peak in the 1 yr having Sh. cordifolia suggested hybrid vitality in between-tree crosses. The consequences away from nearest-next-door neighbor mating ranged among trees and variety; the latest suggest exercise cost of nearby-neighbor mating relative to mating having modestly so much more distant locals try 45% to have S. rubicundum and you will 0% getting Sh professionnels célibataires d’élite. cordifolia. Having said that, new fitness aftereffects of ranging from-forest crossing was indeed reasonable both for varieties (52 and you will 70% according to within this-forest crosses for the very same one or two variety). Crossing consequences decreased between your amounts regarding fruit set and you will step one-yr-old seedling size; precisely the former try significant for both variety. Efficiency indicate a powerful possibility biparental inbreeding anxiety inside tree forest communities and you may limited reproductive separation among woods occupying the rest tree reserves into the Sri Lanka’s wet zone.

Inbreeding anxiety is commonly quoted as an unavoidable result of anthropogenic disturbance to warm forests (e.grams., tree fragmentation, logging), where idea predicts that normal mating models contained in this currently lower-density tree populations was shifted so you can prefer short-distance crosses. To date, not, the consequences away from elevated near-neighbor mating to own inhabitants exercise during the warm woods have but really to become quantified empirically. Two fundamental concerns getting handled is actually: Create people end maturing seeds derived from near-neighbors crosses and you may, if not, exactly how complement are near-neighbor-derived progeny according to anyone else? This research assesses the consequences of near-neighbor mating in two tropical tree kinds in person using fitness contrasting regarding crosses ranging from nearby locals with crosses of a great deal more faraway friends.

Shorea cordifolia (Dipterocarpaceae) is a locally abundant main canopy varieties you to flowers greatly at unpredictable supra-annual durations (We. A beneficial. U. N. Gunatilleke ainsi que al., unpublished study). Plants of species was white and you may brief-stayed, and also the winged fruits was dispersed from the cinch otherwise the law of gravity. Because of its extremely minimal seeds dispersal, genetic relatedness certainly one of near natives in the sheer forest is expected so you can getting highest. During the logged tree at Sinharaja, Sh. cordifolia usually takes place in clumps from ?5–20 adults, intermixed with faster stems (personal observance).

Investigation studies

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%, Fstep one,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 (F1,58 = 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, F1,a dozen = 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.

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