Sexual size dimorphism (SSD), the difference in body size between males and females, is shaped by sexual and natural selection and often varies across populations due to environmental factors. We investigated SSD in the European stag beetle (Lucanus cervus) across three adjacent oak-forested landscapes in northern Latium, Italy. The three forest sites differ in their size, tree maturity, and landscape composition: Macchia Grande di Manziana (MANZ) is a mature, well-preserved forest with large oak-dominated trees; Montevirginio (MONT) is a mosaic of younger coppice forests and oak tree hedgerows due to periodic cutting; and Oriolo Romano (ORIO) consists of small hedgerows along rural paths, with a landscape similar to MONT but with less forested coverage. We assessed elytra and mandible length differences between sexes, interannual variability, and determined whether these variables correlated with tree size. Males consistently had longer elytra than females, with the degree of SSD varying significantly among the sites and years. The largest SSD was observed in MANZ while more moderate SSD occurred in MONT and ORIO. Male mandible length, a key sexually selected trait, was significantly larger in MANZ, with a strong positive correlation with tree size. Male elytra was also related to tree size. These findings highlight the influence of habitat quality, particularly tree size, in shaping SSD and sexually selected traits. Larger trees likely provide better larval habitats, fostering better growth. This study underscores the critical importance of conserving mature forests with larger trees to maintain stag beetle populations and preserve their natural morphological diversity. Future research should investigate additional ecological and genetic factors affecting SSD variation.
Tag: forest trees
Balancing supply and demand: A case study of rattan in the Danau Sentarum national park, West Kalimantan, Indonesia
The Danau Sentarum National Park (DSNP), Kalimantan, Indonesia, covers 30 000 ha of lake and 81 000 ha of lowland, seasonally flooded forest. It is the largest network of inland lakes in Borneo. The park is inhabited by over 5500 Malay fishermen. Most of the fishing implements used by the local population are made from rattan, and large quantities of rattan are also harvested and sold to timber companies for lashing together rafts of logs. The 3 most commonly used species at DSNP are duri antu (Calamus schistoacanthus), duri tapah (Calamus tapa) and duri pelanduk (Ceratolobus hallierianus). Inventories indicate that the 3 rattans differ greatly in the number of harvestable clumps/ha (>4.0 m tall). The duri antu populations average over 900 clumps/ha, duri pelanduk grows at densities of 400-500 clumps/ha, and duri tapah averages only 50 clumps/ha. Based on the observed relationship between clump height and the number of canes/clump, it is estimated that there are over 34 000 duri antu canes/ha growing in the flooded forest of DSNP. An analysis of local demand, productivity and current harvest intensities reveals that local rattan resources are being gradually overexploited. Several fishing communities have started to manage their rattan resources by controlling harvests and rehabilitating and enriching natural stands.
Ecology and management of tropical secondary forest: science, people and policy: proceedings of a conference held at CATIE, Costa Rica, November 10-12, 1997
The disturbance and destruction of the old-growth forests of the tropics continue to monopolize attention in international fora and the popular media, but a steadily growing land area is covered by secondary forest developing on sites which have been deforested and then abandoned by their owners. The natural process of secondary forest succession offers hope that the unique combination of goods and services provided by the original old-growth forests may be at least partially recovered. An enormous number of questions concerning secondary tropical forests and their potential role in sustainable land management and biodiversity conservation remain to be answered, however. Many of these questions are biological and ecological: What are the factors that bring about successional change in vegetation? How does biodiversity change during succession, does its similarity to the biodiversity of old-growth forests increase over time and why, or why not? How might secondary forests be manipulated to optimize their value for a given set of management objectives? Many more questions nevertheless concern people and their actions: what factors bring about land abandonment? How are secondary forests perceived and utilized by rural people? What market or policy changes may contribute to a more profitable and sustainable use of secondary forests? This volume contains 16 papers presented at a conference which brought together researchers concerned with biological, ecological, social/organizational, financial/economic and political aspects of secondary forests and their management with a strictly neo tropical focus. Although the biophysical side of secondary forest research dominated this conference, it is becoming clear that sound management of this resource will depend on interdisciplinary approaches.
Trees, tree genetic diversity and the livelihoods of rural communities in the tropics
This study, prepared within the ambit of The State of the World’s Forest Genetic Resources, reviews what is known about the value of trees for tropical rural communities. It focuses on non-timber products harvested from trees in natural and managed forests and woodlands, the various products and services obtained from trees planted or retained in agroforestry systems, and the commercial products of tree commodity crops. The role of intra-specific genetic variation in determining the value of trees in supporting livelihoods is discussed in each of the three contexts. The study also identifies specific points that should be given particular attention in the future to better support tree-based livelihoods of rural communities in the tropics.
Economic opportunities for smallholders to combine pulpwood trees and food crops
Input/output data from tree growing experiments in Southeast Asia were analysed within the framework of a model of a smallholder farm. Data on cropping were obtained from surveys of farmers. Prior to formulating a whole farm model, this input/output data were modified in two ways: (a) a yield penalty was imposed upon a continuous cropping regime to reflect the impact of land degradation; (b) an agroforestry (intercropping) activity was synthesised by reference to an existing agroforestry bioeconomic model. The modelling framework was conventional linear programming. The interplay of land area availability, land and labour productivity, and interest rates lead to a relatively complex picture, even for the simplified farming systems that were examined. Model results showed a clear indication of the potential role of trees, but this potential role decreased with increasing interest rates. The analysis suggested that smaller farms will be less inclined towards tree growing. A mixture of trees and crops appears attractive, on purely economic grounds, over a wide range of interest rates and land areas. Consideration of factors outside the model, such as risk aversion objectives of smallholders, and their limited opportunities to borrow for investments in tree planting, reinforce the tendency to combine trees and crops.
Public expenditure on trees on farms and sustainable management of natural resources in Uganda from 2015 to 2020
This report presents findings from an assessment conducted on selected key votes, namely those relating to the Ministry of Water and Environment (MWE), the National Forestry Authority (NFA), the Ministry of Agriculture, Animal Industry and Fisheries (MAAIF) and the National Agricultural Advisory Services (NAADS). It is based on approved work plans and budget allocations to the votes, programmes and sub-programmes from 1 July 2015 to 30 June 2020.
This technical report highlights total budget allocations within the two above-mentioned ministries and their agencies in relation to their allocated budget shares towards the financing of sustainable resource management activities on the agricultural landscape in general, and the financing of trees on farms in Uganda over the past 5 years.