SPATIAL FLOWER PARAMETERS AND INSECT SPATIAL VISION

The present article reviews recent and older literature on the spatial parameters that flowers display, as well as on the capacities of anthophilous insects to perceive and use these parameters for optimizing their foraging success. Although co-evolution of plants and pollinators has frequently been discussed with respect to floral colours and insect colour vision, it has rarely been assessed with respect to insect spatial vision and spatial floral cues, such as shape, pattern, size, contrast, symmetry, spatial frequency, contour density and orientation of contours. This review is an attempt to fill this gap. From experimental findings and observations on both flowers and insects, we arrive at the conclusion that all of the spatial and spatio-temporal parameters that flowers offer are relevant to the foraging task and are tuned to the insect's visual capacities and visually guided behaviour. We try, in addition, to indicate that temporal cues are closely related to spatial cues, and must therefore be included when flower–pollinator interactions are examined. We include results that show that colour vision and spatial vision have diverged over the course of evolution, particularly regarding the processing of spatio-temporal information, but that colour vision plays a role in the processing of spatial cues that are independent of temporal parameters. By presenting this review we hope to contribute to closer collaboration among scientists working in the vast fields of botany, ecology, evolution, ethology and sensory physiology.     

Oxypetalum banksii subsp. banksii: a taxon of Asclepiadaceae with an extragynoecial compitum

 The floral morphology of seven Oxypetalum species and, in particular, the spatial relationship between the five stigmatic chambers and two separate ovaries of their flowers with respect to transmission of the pollen tube are studied. In all species, except O. banksii subsp. banksii, floral morphology is similar to that in other Asclepiadeae, and the flowers pollinated with one pollinium develop only one follicle, which means compitum absence. In O. banksii subsp. banksii flowers, the secretory interstaminal tissue lines the inner walls of the stigmatic chambers as in the other species studied, but it also reaches the upper part of the inner surface of the filament tube, where it surrounds the styles, an unprecedented feature for Asclepiadaceae. This tissue secretes nectar and mucilage; the latter acts as transmitting medium for the growth of pollen tubes from pollinia inserted and hydrated in stigmatic chambers (“hyperstigmas”). Mucilage also functions as an extragynoecial compitum: in flowers pollinated with one pollinium both carpels develop into a follicle. Received August 28, 2001; accepted April 9, 2002 Published online: October 14, 2002 Addresses of the authors: Milene Faria Vieira (e-mail: mfvieira@mail.ufv.br), Departamento de Biologia Vegetal, Universidade Federal de Vi?osa, 36571-000, Vi?osa, Minas Gerais, Brazil. George John Shepherd, Departamento de Botanica, Instituto de Biologia, Universidade Estadual de Campinas, C.P. 6109, 13083-970, Campinas, S?o Paulo, Brazil.     

Complex Genetic Effects on Early Vegetative Development Shape Resource Allocation Differences Between Arabidopsis lyrata Populations

Costs of reproduction due to resource allocation trade-offs have long been recognized as key forces in life history evolution, but little is known about their functional or genetic basis. Arabidopsis lyrata, a perennial relative of the annual model plant A. thaliana with a wide climatic distribution, has populations that are strongly diverged in resource allocation. In this study, we evaluated the genetic and functional basis for variation in resource allocation in a reciprocal transplant experiment, using four A. lyrata populations and F₂ progeny from a cross between North Carolina (NC) and Norway parents, which had the most divergent resource allocation patterns. Local alleles at quantitative trait loci (QTL) at a North Carolina field site increased reproductive output while reducing vegetative growth. These QTL had little overlap with flowering date QTL. Structural equation models incorporating QTL genotypes and traits indicated that resource allocation differences result primarily from QTL effects on early vegetative growth patterns, with cascading effects on later vegetative and reproductive development. At a Norway field site, North Carolina alleles at some of the same QTL regions reduced survival and reproductive output components, but these effects were not associated with resource allocation trade-offs in the Norway environment. Our results indicate that resource allocation in perennial plants may involve important adaptive mechanisms largely independent of flowering time. Moreover, the contributions of resource allocation QTL to local adaptation appear to result from their effects on developmental timing and its interaction with environmental constraints, and not from simple models of reproductive costs.     

Floral biology and pollinators of three co-occurring Cistus species (Gistaceae)

BOSCH, J., 1992. Floral biology and pollinators of three co-occurring Cistus species (Cistaceae). The pollination of three species of Cistus, Cistus albidus L., Cistus salvifolius L. and Cistus monspeliensis L. is studied. Insect visitors were censused and some were captured to analyse pollen distribution on their bodies. Floral phenology, breeding systems, some aspects of floral biology (pollen and nectar production, pollen-ovule ratios) and floral morphology were also studied for each species. Flowers of C. albidus produce more pollen and nectar than the other two species studied, and attract more insects, especially those with higher nutritional requirements. All three species are highly self-incompatible, but C. salvifolius and C. monspeliensis show some features that hinder xenogamy, and they have lower pollen-ovule ratios than C. albidus. As a result, this latter species apparently receives higher levels of cross-pollination, but at the cost of a higher investment to attract and reward reliable pollinators.     

Cell division study in ‘pollen mother cells’ and ‘pollen grains’ of in vivo and ex vitro plants in Drimiopsis botryoides

The various normal and abnormal stages of meiosis and pollen mitosis of Drimiopsis botryoides are described, and a comparison between naturally propagated in vivo and tissue culture derived ex vitro plants in respect to their cytological behaviour presented. We also describe the floral morphology and investigate the relationship between the floral developmental stages and the progression of microgametogenesis. In total, 33 bivalents are observed in diakinesis, which indicate the diploid number 2n = 66 and this number is cross-checked by a haploid set of n = 33 chromosomes in pollen mitosis. Only 6.8% and 4.9% meiotic abnormalities were recorded on in vivo and ex vitro plants, respectively, which led to the formation of non-viable pollen. Finally, the microspores have to develop into tri-cellular male gametophyte. Only 0.2% pollen grains are found with a micro-nucleus. Though the higher pollen viability was recorded on both in vivo (89.3 ± 4.1%) and ex vitro (92.1 ± 4.6%) plants, but surprisingly the pollen germination rate is extremely low with 13.6 ± 1.74% and 21.3 ± 1.55%, respectively. The present study obviously enriches the cytological database of D. botryoides and may help future research on androgenesis and genetic improvement.     

Evidence for the effect of serotonin receptor 1A gene (HTR1A) polymorphism on tractability in Thoroughbred horses

Tractability, or how easily animals can be trained and controlled, is an important behavioural trait for the management and training of domestic animals, but its genetic basis remains unclear. Polymorphisms in the serotonin receptor 1A gene (HTR1A) have been associated with individual variability in anxiety‐related traits in several species. In this study, we examined the association between HTR1A polymorphisms and tractability in Thoroughbred horses. We assessed the tractability of 167 one‐year‐old horses reared at a training centre for racehorses using a questionnaire consisting of 17 items. A principal components analysis of answers contracted the data to five principal component (PC) scores. We genotyped two non‐synonymous single nucleotide polymorphisms (SNPs) in the horse HTR1A coding region. We found that one of the two SNPs, c.709G>A, which causes an amino acid change at the intracellular region of the receptor, was significantly associated with scores of four of five PCs in fillies (all Ps < 0.05) and one PC in colts (P < 0.01). Horses carrying an A allele at c.709G>A showed lower tractability. This result provides the first evidence that a polymorphism in a serotonin‐related gene may affect tractability in horses with the effect partially different depending on sex.     

Reproductive biology and pollinators in two enantiostylous Qualea species (Vochysiaceae) in the Brazilian Cerrado

• Enantiostyly is a floral polymorphism in which two floral forms in the same species differ in deflection of the stigma to right or left position. In monomorphic enantiostylous plants, flowers of the two morphs occur within the same individual, usually in the same proportion. In self‐compatible species the function of monomorphic enantiostyly is proposed to increase outcrossing rates and offer a reproductive advantage under pollination limitation. Enantiostylous species are usually self‐compatible and show heteranthery, with poricide anthers and pollen as pollinator reward; however, there are families, such as Vochysiaceae, that have different characteristics.
• We analysed the reproductive system and pollination biology of Qualea parviflora and Q. multiflora, two enantiostylous species from the Brazilian Cerrado that have specific morphological and physiological traits. For this, we characterized flower traits, performed hand pollinations and studied floral visitors.
• We found no differences between morphs in the proportion of flowers, nectar produced or its concentration, pollen quantity and fruit set. Both species were self‐incompatible and quite generalist regarding floral visitors.
• Enantiostyly in self‐incompatible plants seems to confer a reproductive advantage by reducing self‐interference resulting from stigma clogging. This novel result helps to expand our knowledge on this complex floral polymorphism and opens new avenues for future research on this topic.

     

The effectiveness of flower strips and hedgerows on pest control,pollination services and crop yield: a quantitative synthesis

Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.