Pollination ecology, genetic diversity and selection on nectar spur length inPlatanthera lacera(Orchidaceae)

Abstract

Platanthera lacera (Orchidaceae) is a moth-pollinated, loess prairie orchid producing a raceme of one to many whitish-green flowers. Field studies on a western Illinois population found the crepuscular visiting noctuid moth, Anagrapha falcifera (Noctuidae), to be the most frequent pollinator with occasional visits from Allagrapha aerea (Noctuidae). Visitation rates, assessed by removal of at least one pollinium, were relatively high (84.9%) and fruit production on experimentally outcrossed flowers (94.4%) was higher than open-pollinated plants (71.4%). Experimental pollination showed P. lacera to be highly self-compatible (94.1%) with a low level of autogamy (8.2%). Measurements taken from 598 spurs on 44 plants indicated that nectar spur length varied significantly among plants (10.9-17.1 mm, mean 14.3 mm), but was not under selective pressure from visitation by An. falcifera (mean proboscis length 11.1 mm). The absence of selective pressure on nectar spur length is likely to be explained by occasional pollinating visits from Al. aerea (proboscis length 18 mm) and a limited amount of autogamy. Electrophoretic analysis of 12 enzymes revealed seven polymorphic loci. Mean levels of heterozygosity were H e = = = = 0.3384, H o = = = = 0.3229 and F = = = = 0.0458, indicating that P. lacera is primarily an outcrossing species dependent on noctuid moth pollination.

Genetic diversity of the endangered and narrow endemic Piperia yadonii (Orchidaceae) assessed with ISSR polymorphisms

“…The program PHYLIP version 3.67 was used to perform these analyses. Limited pollen and seed dispersal due to habitat fragmentation were also identifi ed as the major factors causing high among population differentiation in Changnienia amoena ( Li and Ge, 2006 ), despite loci, has also been reported in populations of the primarily outcrossing orchids Cephalanthera longifolia ( Chung et al, 2004 ), Oncidium hookerii ( Alcantara et al, 2006 ), Platanthera lacera ( Little et al, 2005 ), and P. leucophaea ( Wallace, 2002 ). fl owering.…”

Flies and Flowers in Darwin's Race

“…Darwin's hypothesized mechanism has not been verified. Several researchers have explored the nature of selection operating on long‐tubed flowers, and have found that individuals with longer tubes do sometimes have higher reproductive success (Nilsson 1988; Herrera 1993; Maad 2000; Alexandersson and Johnson 2002; Little et al 2005). These studies show that proboscis length can act as a selective agent on floral tube length.…”

Floral miniaturisation and autogamy in boreal-arctic plants are epitomised by Iceland’s most frequent orchid,Platanthera hyperborea

“…Thus far, the emphasis has been placed on adaptations for insect-mediated allogamy, most commonly involving moths (e.g., Darwin, 1877; Nilsson, 1983; Maad & Nilsson, 2004; Little, Dieringer & Romano, 2005; Boberg et al, 2014). Indeed, the P. dilatata-hyperborea group encompasses multiple reproductive strategies, many members being pollinated primarily as a result of offering nectar rewards to various noctuid moths (Luer, 1975; Hapeman & Inoue, 1997; Sheviak, 2002).…”