High Density Of Individuals Research Articles

Within-gap position shapes fifty years of forest dynamics in a temperate hardwood forest in Connecticut, USA

Predictions of forest succession have a tremendous influence on forest management decisions, strategies, and policies. Although generalized forest succession models are intensively studied, there is a distinct lack of long-term studies confirming these models due to the logistical constraints of tracking a forest as it develops over decades or centuries. Here we use a long-term dataset spanning >50 years of third-growth forest development in experimental forest gaps within a second-growth northern temperate hardwood forest to examine the influence of gap position on the structure and composition of regeneration and confirm past models of forest succession. We document key stand development patterns in even-aged mixed-species stands, including vertical stratification and shifts in diameter distributions. While the stands have shifted into a classic inverse-J diameter distribution, these shifts are due to a combination of unimodal distributions of the shade-intolerant and intermediate guilds that grow in mean diameter over time with consistently high densities of small individuals from the shade-tolerant guild. The greatest vertical stratification between the shade-intolerant and intermediate guilds occurred 30 years after clearing but then disappeared as the intermediate guild increased in height. In contrast, the separation in strata between the shade-tolerant species and the more intolerant guilds only increased over time. Finally, we found that gap position had a significant effect on productivity. The basal area, height, and species richness (in this case, an indicator of canopy stratification) were best modeled with negative quadratic regressions with highest values in gap centers and lower values towards the edges of gaps. This pattern aligns more with expected moisture and nutrient availability within gaps than expected solar radiation in the northern hemisphere, suggesting that moisture and nutrient availability may play a greater role than is often acknowledged in temperate forest types. Furthermore, these relationships were readily apparent only after 30 years yet became more accentuated with time, highlighting the importance of long-term research on successional dynamics for management. Ultimately our results document a clear successional trajectory in these gaps that follow expectations for even-aged mixed-species stand development where a full suite of species leads to rolling periods of dominance based on species functional guilds, with early successional species replaced by late-successional species in the progression of succession.

Risk assessment for airborne disease transmission by poly-pathogen aerosols.

In the case of airborne diseases, pathogen copies are transmitted by droplets of respiratory tract fluid that are exhaled by the infectious that stay suspended in the air for some time and, after partial or full drying, inhaled as aerosols by the susceptible. The risk of infection in indoor environments is typically modelled using the Wells-Riley model or a Wells-Riley-like formulation, usually assuming the pathogen dose follows a Poisson distribution (mono-pathogen assumption). Aerosols that hold more than one pathogen copy, i.e. poly-pathogen aerosols, break this assumption even if the aerosol dose itself follows a Poisson distribution. For the largest aerosols where the number of pathogen in each aerosol can sometimes be several hundred or several thousand, the effect is non-negligible, especially in diseases where the risk of infection per pathogen is high. Here we report on a generalization of the Wells-Riley model and dose-response models for poly-pathogen aerosols by separately modeling each number of pathogen copies per aerosol, while the aerosol dose itself follows a Poisson distribution. This results in a model for computational risk assessment suitable for mono-/poly-pathogen aerosols. We show that the mono-pathogen assumption significantly overestimates the risk of infection for high pathogen concentrations in the respiratory tract fluid. The model also includes the aerosol removal due to filtering by the individuals which becomes significant for poorly ventilated environments with a high density of individuals, and systematically includes the effects of facemasks in the infectious aerosol source and sink terms and dose calculations.

Associated health and social determinants of mobile populations across HIV epidemic gradients in Southern Africa

BackgroundGrowing travel connectivity and economic development have dramatically increased the magnitude of human mobility in Africa. In public health, vulnerable population groups such as mobile individuals are at an elevated risk of sexually transmitted diseases, including HIV. MethodsThe population-based Demographic Health Survey data of five Southern African countries with different HIV epidemic intensities (Angola, Malawi, South Africa, Zambia, and Zimbabwe) were used to investigate the association between HIV serostatus and population mobility adjusting for socio-demographic, sexual behavior and spatial covariates. ResultsMobility was associated with HIV seropositive status only in Zimbabwe (adjusted odds ratio [AOR] = 1.37 [95% confidence interval [CI]: 1.01–1.67]). These associations were not significant in Angola, Malawi, South Africa, and Zambia. Females had higher odds of mobility than males in Zimbabwe (AOR = 1.37, CI: 1.10–1.69). The odds of mobility decreased with age in all five countries. ConclusionsOur findings highlight the heterogeneity of the social and health determinants of mobile populations in several countries with different HIV epidemic intensities. Effective interventions using precise geographic focus combined with detailed attribute characterization of mobile populations can enhance their impact especially in areas with high density of mobile individuals and high HIV prevalence.

Antlions in interaction: confrontation of two competitors in limited space

Abstract The study focused on the behaviour of sit-and-wait antlion larvae in interspecific interactions. Antlion larvae usually occur in clusters with a high density of individuals; therefore, competition can be intense. We observed two abundant antlion species, E. nostras and M. formicarius, which co-occur in some habitats. In a simple habitat choice experiment where substrates differed according to sand particle size, we found that E. nostras exhibited dominance over M. formicarius. Most E. nostras larvae remained in the more suitable substrate and constructed pits, while all the M. formicarius larvae moved out of the suitable area, and did not build pits. In the second experiment, we observed the characteristics of the pit-fall traps and scored the occurrence of larval relocation in relation to interactions and in the control group, where larvae were kept in containers separately. In interactions, the larvae of E. nostras constructed smaller pits, but pit enlargement was greater in comparison to the control group. M. formicarius larvae constructed similar sized pits in both groups; however, enlargement was greater in the control group. Relocation of larvae occurred only during interactions. In direct interactions, we found 15 behavioural patterns, which are described in detail for the first time. In the presence of a competitor, larvae showed intense territorial behaviour. We recorded several behavioural patterns during larval confrontation, and interestingly, intraguild predation rarely occurred. In most cases, E. nostras larvae outcompete M. formicarius, which was evident from the larger pits and the rate of pit-construction.

High Species Diversity of the Family Dipterocarpaceae in Mursala Island, Indonesia

Known to have a long history of timber extraction, Mursala Island on the west coast of North Sumatra Province is a small island home to the endemic tree Dipterocarpus cinereus and many other Dipterocarpaceae species. In the present study, distance sampling using line-transect was used to assess the species diversity and population status of Dipterocarpaceae species on the Island. A total of 26 Dipterocarpaceae species from 6 genera was identified from Mursala Island. The genus that was represented by the highest number of species was Shorea (13 species), followed by Vatica (5), Dipterocarpus (4), Hopea (2), Cotylelobium (1) and Dryobalanops (1). Among these, two Mursala Island endemic were identified: D. cinereus and H. bancana. Furthermore, according to IUCN Red List category, 11 species (42.3%) were classified as critically endangered, four species (15.4%) were of endangered, 5 species (15.2%) were of vulnerable, one species was of near threatened, 2 species were of least concern and 3 species were not assessed yet. Based on distance analysis, the species with the highest individual density was S. multiflora (21.72±10.96 individual/ha), whereas species with the lowest density was S. johorensis (0.06±0.01 individual/ha). Two main threats for Dipterocarpaceae species in Mursala Island were observed during the survey: illegal logging and habitat conversion. Increasing the protection level of the island was recommended to conserve all the species of Dipterocarpaceae. Besides, providing alternative sources of living for the illegal logger through commercialization of non-timber forest products, ecotourism, and the sustainable fishery was recommended so that they could stop illegal logging activity.

Use of nursery areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes).

Nursery areas are fundamental for the success of many marine species, particularly for large, slow-growing taxa with low fecundity and high age of maturity. Here, we examine the population size-class structure of the extinct gigantic shark Otodus megalodon in a newly described middle Miocene locality from Northeastern Spain, as well as in eight previously known formations (Temblor, Calvert, Pisco, Gatún, Chucunaque, Bahía Inglesa, Yorktown and Bone Valley). In all cases, body lengths of all individuals were inferred from dental parameters and the size-class structure was estimated from kernel probability density functions and Gaussian mixture models. Our analyses support the presence of five potential nurseries ranging from the Langhian (middle Miocene) to the Zanclean (Pliocene), with higher densities of individuals with estimated body lengths within the typical range of neonates and young juveniles. These results reveal, for the first time, that nursery areas were commonly used by O. megalodon over large temporal and spatial scales, reducing early mortality and playing a key role in maintaining viable adult populations. Ultimately, the presumed reliance of O. megalodon on the presence of suitable nursery grounds might have also been determinant in the demise of this iconic top predatory shark.

Aquaculture facilities drive the introduction and establishment of non-native Oreochromis niloticus populations in Neotropical streams

This study investigated whether aquaculture facilities drive the introduction and establishment of the non-native Nile tilapia (Orechromis niloticus) in Neotropical streams, Brazil. Samples were taken from nine streams with different aquaculture occupation intensities (no, moderate, and intense) using the percentage of occupation of micro-watersheds by aquaculture ponds as a proxy for propagule pressure. The presence of aquaculture facilities and the percentage of aquaculture occupation were good predictors of the catch frequency and of densities of tilapias in the adjacent natural environment. In the streams under intense propagule pressure, females prevailed and high densities of young individuals comparing to adults were recorded. It suggests that the species was reproductively successful in the natural environment. In the streams under moderate propagule pressure, males prevailed, which indicates the likely capture of individuals escaped from aquaculture facilities. In general, our results show the positive influence of propagule pressure on the introduction and establishment of Nile tilapia in natural ecosystems, showing that aquaculture expansion of O. niloticus poses a threat to the conservation of aquatic biodiversity.

Prospects of the classic method of forest restoration by planting seedlings: a review

This paper aims to present a literature review highlighting the perspectives of classical method of forest restoration through planting seedlings, addressing advantages, disadvantages, and ecological implications of the technique, compared to nucleation techniques. When ecosystems are altered, restoration can be accomplished using forest restoration methods. The first initiatives used standard random planting of trees, without defined spacing. After, restoration plantings have become mixed with native species, combining different species according to their characteristics or role in succession, and may be performed in islands of diversity or lines. The first consists of planting seedlings in small nuclei with high diversity and density of individuals of different ecological groups. total area in-line planting can be done by direct seeding or planting seedlings. In this case, combinations of species from different ecological groups planted in rows can be performed. However, the classical method of planting seedlings, although widely disseminated and playing an important role in biodiversity conservation, does not include system processes as a whole, compromising the ecosystem ecological sustainability. On the other hand, the use of nucleation techniques enables the occurrence of primary and secondary processes of ecological succession by adding diversity of species and different life forms to the system, complicating relations with small energy input contrived.

Diversity of Flora as Affected by Time Consequences of Revegetation Age in Post Coal Mine Area at PT Berau Coal Tbk, East Kalimantan Indonesia

This study aims to examine the diversity of flora in various age classes of revegetation of post-mining coal. This research was conducted at PT. Berau Coal, Binungan block, East Kalimantan. Sampling plots were applied on revegetation land of post-mining coal aged 0, 2, 4, 6, 8 and 10 years, and natural forest as a control. Flora observations were carried out on sample plots of size 25m x 40m for sapling, poles and trees, while sub-plots 1m x 1m for seedlings and understorey. In natural forests observations were made on sample plots measuring 20m x 20m for trees with sub plot 2m x 2m for uderstorey and seedlings, 5m x 5m for saplings, 10m x 10m for poles. The analysis results show that the highest individual density per ha is found in natural forests (seedlings, saplings and poles). The highest of flora index of diversity, richness and evenness were found in natural forests. The flora from revegetation of eight-year has been able to approach to natural forests conditions. The species of plants that predominate in some revegetation age classes are Rhynchospora corymbose (understorey), Senna siamea (seedling, sapling, pole and tree). Acacia mangium and Macarangan hypleoca grow naturally in some revegetation age.

Temporal Changes in Number of Breeding Individuals of the Amami Tip-Nosed Frog

Abstract: Amami tip-nosed frog (Odorrana amamiensis) is an endangered species endemic to Amami-Oshima Island and Tokunoshima Island, in Japan. This species is threatened by invasive species and habitat destruction. Although action is needed to protect them, the breeding ecology of O. amamiensis is poorly understood. A better understanding of its breeding ecology would contribute to conservation efforts. This study reports temporal changes in number of O. amamiensis breeding individuals in Kinsakubaru area, Amami-Oshima Island from the 28 Nov. 2015 to the 5 Dec. 2015. A 20 m transect line was set at a stream to count the number of O. amamiensis individuals at night and during daytime for eight days. Over 200 individuals were observed and many of them were breeding with lively mating calls around the small stream at night for three days. The high density of individuals decreased rapidly afterwards. This is the first report quantifying the temporal changes in number of breeding individuals of O. amamiensis. The species is usually nocturnal, but some individuals were observed at breeding sites during the daytime as well. Field research on O. amamiensis is usually conducted at night, but it can be risky because the nocturnal poisonous snake Habu (Protobothrops flavoviridis) also inhabits Amami-Oshima Island. The results suggested that field research during daytime was relatively safer and perhaps an easier approach to find breeding sites of O. amamiensis compared to searching at night.

Caracterización estructural de una comunidad arbórea de un sistema silvopastoril en una zona de transición florística de Nuevo León

Las comunidades arbóreas con sistemas silvopastoriles desempeñan un papel importante en los ecosistemas áridos y semiáridos del país, al conservar la biodiversidad y el desarrollo de las actividades ganaderas, que son de vital importancia en el norte de México. Con el objetivo de caracterizar una comunidad arbórea de un sistema silvopastoril en una zona de transición de matorral espinoso tamaulipeco y mezquital en Nuevo León, se establecieron cinco sitios de muestreo de 2500 m2, en los cuales se realizó un inventario de todas las especies arbóreas con diámetro a la altura de 1.30 m (DAP) igual o mayor que 7.5 cm. Se evaluaron composición y estructuras vertical y horizontal a través de parámetros estructurales de la vegetación (abundancia relativa, frecuencia relativa, dominancia relativa), índice de valor de importancia, índice de valor forestal y modelos para las variables diámetro normal - área de copa. Las especies principales desde el punto de vista ecológico fueron Prosopis laevigata (Hump. & Bonlp. ex. Willd.) M. C. Johnst. y Ebenopsis ebano (Berland.) Barneby & J. W. Grimes, la comunidad presentó alta densidad de individuos, alta cobertura de copa y una estructura vertical con alta proporción de individuos con altura mayor o igual a 6 m. El modelo lineal mostró los mejores ajustes al presentar un R2 = 0.621. El manejo silvo-pastoril ha conservado y promovido los atributos estructurales de la comunidad vegetal nativa.

Automated tracking and analysis of ant trajectories shows variation in forager exploration

Determining how ant colonies optimize foraging while mitigating pathogen and predator risks provides insight into how the ants have achieved ecological success. Ants must respond to changing resource conditions, but exploration comes at a cost of higher potential exposure to threats. Fungal infected cadavers surround the main foraging trails of the carpenter ant Camponotus rufipes, offering a system to study how foragers behave given the persistent occurrence of disease threats. Studies on social insect foraging behavior typically require many hours of human labor due to the high density of individuals. To overcome this, we developed deep learning based computer vision algorithms to track foraging ants, frame-by-frame, from video footage shot under the natural conditions of a tropical forest floor at night. We found that most foragers walk in straight lines overlapping the same areas as other ants, but there is a subset of foragers with greater exploration. Consistency in walking behavior may protect most ants from infection, while foragers that explore unique portions of the trail may be more likely to encounter fungal spores implying a trade-off between resource discovery and risk avoidance.

Short Communication: Diversity and distribution of figs (Ficus spp.) across altitudes in Gunung Tilu, Kuningan, West Java, Indonesia

Abstract. Hendrayana Y, Widodo P, Kusmana C, Widhiono I. 2019. Short Communication: Diversity and distribution of figs (Ficus spp.) across altitudes in Gunung Tilu, Kuningan, West Java, Indonesia. Biodiversitas 20: 1568-1574. The genus of Ficus is significant component in tropical rainforest ecosystem, consisting of large number of species and spreading across altitudes. This research was aimed to examine the diversity and distribution of species belong to Ficus genus in Gunung Tilu, Kuningan District, West Java as a basis for building conservation strategies. There were 12 species of Ficus found from the altitudes of 600 to 1000 m asl. The highest number of species was found at the altitudes of 600 - 700 m above sea level with 10 species, while the lowest number of species were found at the altitudes above 1000 m asl with only two species. The highest individual density was found at an altitude of 600 m asl, while the lowest density was at the altitude of 1000 m asl. The distribution pattern of Ficus spreads throughout the region of Gunung Tilu, Kuningan.

Towards UNAIDS Fast-Track goals: targeting priority geographic areas for HIV prevention and care in Zimbabwe.

Zimbabwe has made substantial progress towards the Joint United Nations Programme on HIV/AIDS (UNAIDS) targets of 90-90-90 by 2020, with 73% of people living with HIV diagnosed, 87% of those diagnosed on antiretroviral therapy (ART) and 86% of those on ART virally suppressed. Despite this exceptional response, more effort is needed to completely achieve the UNAIDS targets. Here, we conducted a detailed spatial analysis of the geographical structure of the HIV epidemic in Zimbabwe to include geographical prioritization as a key component of their overall HIV intervention strategy. Data were obtained from Zimbabwe Demographic and Health Survey (ZDHS) conducted in 2015 as well as estimations from the Zimbabwe Population-Based HIV Impact Assessment (ZIMPHIA) 2016 report, and other published literature. Data were used to produce high-resolution maps of HIV prevalence. Using these maps combined with the population density maps, we mapped the HIV-infected population lacking ART coverage and viral suppression. HIV maps for both sexes illustrated similar geographical variation of HIV prevalence within the country. HIV-infected populations lacking ART coverage and viral suppression were concentrated in the main cities and urban settlements such as Bulawayo, Harare, Ruwa and Chitungwiza. Our study showed extensive local variation in HIV disease burden across Zimbabwe for both women and men. The high-resolution maps generated here identified areas wherein high density of HIV-infected individuals are lacking ART coverage and viral suppression. These results suggest that there is need to tailor HIV programmes to address specific local needs to efficiently achieve epidemic control in Zimbabwe.

STORM-INDUCED COMMUNITY DYNAMICS IN THE FEZOUATA BIOTA (LOWER ORDOVICIAN, MOROCCO)

In the Central Anti-Atlas (Morocco), the lower part of the Fezouata Shale has yielded locally abundant remains of soft-bodied to lightly sclerotized taxa, occurring in low diversity assemblages characterized by strong spatial and taxonomic heterogeneities, and frequently, by the occurrence of small-sized individuals. Size frequency analyses of Celdobolus sp., Wosekella sp. (both linguliformean brachiopods) and Babinka prima (babinkid bivalve) collected in deposits of the Fezouata Shale and associated with distinct paleoenvironmental conditions show that short-lived communities of epifaunal and shallow infaunal taxa were regularly smothered and killed by distal storm deposits. Small-sized individuals more likely represent juveniles, rather than ‘dwarfed' adults (Lilliput Effect). Consequently, unstable environmental conditions (regular storms, and possibly low oxygenation of the water column) probably explain the unusual community dynamics of late Tremadocian assemblages of the Fezouata Biota (high density of individuals, low α-diversity, and high γ-diversity), interpreted as short-lived, opportunistic populations. This process has wider implications for the understanding of occurrences of small individuals elsewhere in the fossil record.

Clusters of high abundance of plants detected from local indicators of spatial association (LISA) in a semi-deciduous tropical forest.

Plants are rarely randomly distributed across communities, and patchiness is a common spatial pattern in most tropical forests. Clusters of high density of plant individuals are related to internal and external forces, as well as to historical events. The detection of aggregated patterns of plant individuals allows for a better understanding of the internal and external factors that guide the distribution of species. The aim of this research was to detect and characterize clusters of high abundance of plants and species richness in semi-deciduous forests in the Dominican Republic. For this, we collected vegetation data from 575 quadrats in 23 transects (2300 m2 in total) within the Ocoa river basin. Using local Moran’s I statistics, we isolated 18 quadrats of high density of individuals. We show that density of individuals can be 2.5 times larger on average than in non-aggregated quadrats, and can reach higher values for shrubs species as well as for palms and vines species. In addition, we found that shrub species are the most abundant group in aggregated quadrats, and density of tree species is significantly smaller than that of shrub species. High density quadrats are predominantly occupied by shrubs, palms and vines, following patterns of species composition and lithology. Detecting clusters of high density of individuals could help in the efficient assessment of richness in semi-deciduous tropical forests, and may support new conservation practices for this valuable but threatened ecosystem.

Molecular evidence of hybridization in sympatric populations of the Enantia jethys complex (Lepidoptera: Pieridae).

Hybridization events are frequently demonstrated in natural butterfly populations. One interesting butterfly complex species is the Enantia jethys complex that has been studied for over a century; many debates exist regarding the species composition of this complex. Currently, three species that live sympatrically in the Gulf slope of Mexico (Enantia jethys, E. mazai, and E. albania) are recognized in this complex (based on morphological and molecular studies). Where these species live in sympatry, some cases of interspecific mating have been observed, suggesting hybridization events. Considering this, we employed a multilocus approach (analyses of mitochondrial and nuclear sequences: COI, RpS5, and Wg; and nuclear dominant markers: inter-simple sequence repeat (ISSRs) to study hybridization in sympatric populations from Veracruz, Mexico. Genetic diversity parameters were determined for all molecular markers, and species identification was assessed by different methods such as analyses of molecular variance (AMOVA), clustering, principal coordinate analysis (PCoA), gene flow, and PhiPT parameters. ISSR molecular markers were used for a more profound study of hybridization process. Although species of the Enantia jethys complex have a low dispersal capacity, we observed high genetic diversity, probably reflecting a high density of individuals locally. ISSR markers provided evidence of a contemporary hybridization process, detecting a high number of hybrids (from 17% to 53%) with significant differences in genetic diversity. Furthermore, a directional pattern of hybridization was observed from E. albania to other species. Phylogenetic study through DNA sequencing confirmed the existence of three clades corresponding to the three species previously recognized by morphological and molecular studies. This study underlines the importance of assessing hybridization in evolutionary studies, by tracing the lineage separation process that leads to the origin of new species. Our research demonstrates that hybridization processes have a high occurrence in natural populations.

Community structure of soil mites under Quercus variabilis forests in small watershed of karst area, Guizhou, China.

To analyze the differences of community structure of soil mites between the rocky desertification environment and karst beech forests, we investigated the soil mites of Quercus variabilis forest in the Chaoying small watershed of Guizhou Province. Soil mites from 83 genera, 54 families, and 3 orders were collected in the four investigations of 2014. We analyzed the differences of genus numbers, individual numbers, individual density, Shannon diversity index (H), Margalef richness index (SR), Pielou evenness index (J), maturity index (MI) of predatory soil mites (Mesostigmata: Gamasina), community structure of the oribatid mites (MGP) and nutritional structure of mite. Results showed that Oribatida was dominant in taxonomic richness and individual abundance. Abundant genus, high individual density and diversity of soil mites were found in summer and autumn, and higher individual abundance was found in spring and autumn. Soil mites showed surface-aggregation in their distribution. Most predatory mites were K-selected in summer and r-selected in other seasons. The ecological groups of the oribatid mites were mainly P-type and O-type. Hypochthonius, Allobelba and Zygoribatula constituted the nutrient function group of the soil mites. There were significant differences in the main groups of soil mites in the beech forest and other forest types. Among all the groups, Parholaspididae, Laelapidae, Oppiidae and Haplozetidae with abundant genera composition, Multioppia, Parholaspulus, Scheloribates and Haplozetes with predominance could be used as a biological indicator for the soil environment in beech forests.

Lecciones ecológicas de la historia amazónica: impacto diferencial del uso del suelo en las estructuras y biomasas aéreas de bosques secundarios en Napo, Ecuador

Amazonian forests mitigate climate change, are being deforested and recover their structures and functions throughout secondary succession. It is necessary to understand how different land-uses alter such a recovery and why landowners decide to clear-cut some areas while letting others to fallow. That was addressed by counting and measuring all trees of at least 10 cm diameter in four one-hectare plots whose land-use histories were exhaustively reconstructed using ethnographic-historical methods. Plots A (12-15 years old), B (22-25 years old) and C (35-37 years old) were pastures and oligocultures for feeding human populations growing during a period of vigorous oil-exploration; next, food demands changed and plots were abandoned. Plot D (35-40 years old) was used for self-consumption, shifting agriculture (more than 50 planted species), afterwards used and managed for extracting resources during secondary succession. Tree diameters in plots B and C were larger compared to those found in plots A and D –which were similar. The latter suggests that fallow management in plot D kept its forest structurally young, hence, the Amazon may include forests chronologically older than the age suggested by their structures. Similar results were found for total basal area and aboveground biomass, while the high density of individuals in plot D suggests a vigorous gap regeneration. In conclusion: different land-uses are confirmed to alter further succession, and the changes of food demand and food security affect farmer`s decisions on letting forests to recover. Local development planners may take the later into account.

Selective byssus attachment behavior of mytilid mussels from hard- and soft-bottom coastal systems

In both sedimentary and rocky coastal habitats, epibenthic mytilid mussels use byssal threads for attachment to the substratum and to form beds with high densities of individuals. Number and attachment strength of byssal threads can be adjusted according to external factors such as hydrodynamic forces or predators, but it is unknown whether mytilid mussels distinguish between substrata of different quality for byssus attachment in different habitat types. In field studies, we examined the attachment strength of the mussel Perumytilus purpuratus growing on Pacific hard- and soft-bottom shores in Chile and of the blue mussel Mytilus edulis from an Atlantic rocky shore in France and a sedimentary shore in the North Sea (Germany), respectively. In additional laboratory experiments, we studied mussel substratum selectivity of both bivalve species from soft and hard bottoms by offering living versus dead, barnacle-fouled vs. unfouled, and firmly attached vs. loose conspecifics. In the field, attachment strength of P. purpuratus on hard bottoms was substantially higher than on soft bottoms even though mussels produced more byssus in the latter habitat. In contrast, blue mussels M. edulis showed only a slightly reduced attachment strength on soft compared to hard bottoms. In the soft-bottom habitat, fouled individuals from the edge of a blue mussel bed were especially strongly attached. In the byssus attachment behavior experiments, P. purpuratus from both habitats showed a significant preference for living conspecifics and those from soft bottoms preferred firmly attached conspecifics. Blue mussels had no preference for particular conspecifics except those from soft-bottom habitats, which preferred fouled over clean mussels. In general, in the choice experiments hard-bottom M. edulis produced more byssus. Our results confirmed that mytilid mussels may show active substratum choice for byssus attachment, which depends on mussel species and habitat type. The results suggest that mussels are adapted to a particular habitat type, with P. purpuratus showing lower adaptation to soft-bottom areas while M. edulis shows successful strategies for both environments.