In Costa Rica, dioecious Carica papaya has been observed growing in disturbed areas and within secondary lowland forests. Such populations can serve as a reservoir of genetic and morphological diversity for this tropical fruit crop. We quantify the levels and patterns of the diversity of naturally occurring populations of C. papaya and address the demographic history of these populations. We measured 29 vegetative and reproductive morphological traits in situ from 252 plants and found significant heterogeneity among regional populations in the majority of these traits. Significant variation was found among regional populations with respect to fruit size and shape, with plants in the Nicoya Peninsula possessing smaller, less fleshy fruit, a characteristic of previously described wild populations of papaya. We then assessed the levels and patterns of genetic diversity in 164 plants from natural populations and 20 cultivars. Natural populations exhibit a deficiency of heterozygotes; however, this is much more pronounced within the cultivars. Although there is little genetic differentiation among natural populations, we did find evidence of cryptic genetic population structure. Analyses of population demography indicate that these natural populations have undergone a recent genetic bottleneck, followed by recent population expansion, possibly promoted by the transformation of the Costa Rican landscape for agricultural use.Abstract in Spanish is available in the online version of this article.

A manual and software for common statistical methods for ecological and biodiversity studies

Summary1. The objective of this research was to evaluate soil subsurface methods that may aid in seedling establishment and encourage root colonization from a diverse group of ectomycorrhizal (ECM) fungi during restoration projects. 2. American chestnut Castanea dentata Marsh. Borkh. and backcrossed chestnuts seedlings were planted on a reclaimed coal mine site in central Ohio, USA. Roots from chestnut seedlings planted in the plots that were cross-ripped, plowed and disked, or a combination of treatments were sampled for ECM fungi and compared with control plots. The presence and identification of native ECM were determined by fungal DNA sequencing of the internaltranscribed (ITS) region. 3. After two growing seasons, mechanical soil treatments resulted in seedlings with significantly more ECM species when compared to seedlings grown in the control plots (P < 0Á0001). A nonmetric multidimensional scaling ordination followed by a permutational MANOVA confirmed significant dissimilarities in community composition between the control and mechanically treated plots (F = 0Á24, P = 0Á015). 4. Ectomycorrhizal root colonization was significantly higher on the chestnut seedlings sampled from the mechanically treated plots when compared to the control plots (F = 10Á63, P < 0Á0001). Differences did not exist among the three mechanical treatments. There was also a significant increase in above-ground seedling growth in the plots that were treated with a surface soil method (F = 15Á72, P < 0Á0001). It is not clear whether ECM activity was the driver of plant growth; regardless, both are strong indicators of healthy tree establishment. 5. Synthesis and applications. This study illustrates that the use of soil subsurface methods increased ectomycorrhizal (ECM) activity and seedling growth. Employing methods that encourage the root colonization by beneficial ECM and promote healthy seedling establishment may aid the long-term survival of chestnuts in restoration projects. This can be applied to other hardwood seedlings used in reforestation in soils compacted after anthropogenic disturbances.

This study evaluated the influence of planting sites on the establishment and ectomycorrhizal (ECM) colonization of American chestnut (Castanea denetata(Marsh.) Borkh.) on an abandoned coal mine in an Appalachian region of the United States. Root morphotyping and sequencing of the fungal internal transcribed spacer (ITS) region were used to identify the ECM species associated with the chestnut seedlings. Germination, survival, ECM root colonization, and growth were assessed in three habitats: forest edge, center (plots without vegetation), and pine plots (a 10-year-old planting ofPinus virginiana). Seedlings in pine plots had higher survival (38%) than the other plot types (center 9% and forest edge 5%;P=0.007). Chestnuts found colonized by ECM within the pine plots were larger (P=0.02), contributed by a larger root system (P=0.03). Forest edge and pine plots had more ECM roots than seedlings in center plots (P=0.04). ITS fungal sequences and morphotypes found among chestnut and pine matchedScleroderma, Thelephora,andPisolithussuggesting these two plant species shared ECM symbionts. Results indicated that the presence ofP. virginianahad a greater facilitative effect on growth and survival of chestnut seedlings.