Intra-inflorescence variation in reproductive traits of Conopholis alpina (Orobanchaceae) in Tomatlán, Puebla

Itzel L. Castillo-Sánchez, Pedro L. Valverde and Fernando Vite, Departamento de Biología, Universidad Autónoma Metropolitana, Unidad Iztapalapa (UAM-I), Ciudad de México, Mexico, Dulce M. Figueroa-Castro, Laboratorio de Interacciones Ecológicas, Facultad de Ciencias Biológicas, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico

Background/Question/Methods
The existence of variation within inflorescences has been described in several plant families. This phenomenon is known as intra-inflorescence variation. Two hypotheses have been raised to explain such variation: resource availability or inflorescence's vascular architecture. Furthermore, intra-inflorescence variation in plant reproductive traits has been shown to have important effects on plant fitness. Previous study on Conopholis alpina at Lachatao, Oaxaca showed a pattern of intra-inflorescence variation of several reproductive traits where the middle region of the inflorescence has higher values than the base and apex regions. However, it is unknown if the same pattern of intra-inflorescence variation will hold in a different population. The aim of this study was to describe the pattern of intra-inflorescence variation in reproductive traits of C. alpina in Tomatlán, Puebla. In 23 individuals of C. alpine, six floral buds and fruits were collected from each of three different regions within the inflorescence and infructescence (base, middle, and apex), respectively (2 reproductive structures X 3 regions X 23 individuals = 138 reproductive structures). Number and viability of pollen grains, number of ovules, and pollen/ovule ratio (P/O) were estimated from floral buds, whereas fruit length and width, seed number and weight, and seed-set were obtained from fruits. Repeated measures ANOVA analyses were used to establish the effects of the region within the inflorescence on the reproductive traits measured.
Results/Conclusions
Ovule number, fruit length and width, and seed number and weight were significantly higher in reproductive structures from the base and middle regions of the inflorescence than those from the apex. Seed-set did not exhibit differences between regions, and it was high in the three regions of the inflorescence (86.16 - 88.35%), suggesting that the allocation of resources is similar among the three regions of the inflorescence. Our results show a different pattern of variation than the one previously described, suggesting that resource availability is different between sites and that the intra-inflorescence variation in C. alpina is due to competition for resources among the different regions of the inflorescence.