Cloud Forest Remnants Research Articles

Two new species of Pleurothallidinae (Orchidaceae) from cloud forest remnants in the eastern Andes of Colombia

Two new pleurothallid species of the genera Lepanthes and Pleurothallis, native to cloud forest remnants of the Eastern Andes of Colombia, are described and illustrated. Lepanthes pseudoabitaguae is compared with Lepanthes abitaguae, from which it differs by the color of the flowers and by the oblong and biglandular appendix. Pleurothallis falcata is similar to Pleurothallis suspensa, but can be recognized by the falcate to lanceolate leaves, denser inflorescences, longer sepals, and the lip completely recurved with erose apical margins. We also provide comparisons with similar species and offer comments on their ecology. Furthermore, we discuss the significance of this highly anthropized region and its richness in orchid species.

Population ecology and behaviour of two Afrotropical forest butterflies

Over the last decades, numerous natural habitats have been converted into settlement areas, agricultural land, and tree plantations on a large spatial scale. As a result, natural ecosystems have been destroyed. In consequence, many ecosystems exist today as small and geographically isolated remnants. To what extent the original species diversity can persist in such small habitat patches is questionable and strongly depends on the ecology of the species. A prominent example of severe habitat destruction are the species-rich tropical cloud forests of Taita Hills in southern Kenya, which have been deforested almost completely during past decades. However, there still exist typical forest species in the few remaining forest fragments. In this study, we investigate the population ecology and behaviour of two butterfly species present in the cloud forest remnants of Taita Hills, Protogoniomorpha parhassus and Precis tugela. Over a period of one month, we conducted Mark-Release-Recapture to study population sizes and demographic structures, lifespan, dispersal, and behaviour. We found that both species exhibited medium population sizes and are sedentary. However, some individuals performed dispersal throughout the forest. The behaviour of the two species differs: While P. tugela was mostly observed basking with open wings, P. parhassus was mostly sitting under leaves with closed wings. The life span was rather long for butterflies.Implications for insect conservationThis study documents the population ecology and behaviour of these two Afrotropical butterflies and underlines the relevance of the conservation of cloud forest remnants to preserve species, which mainly depends on these habitat remnants.

Regeneration Status and Role of Traditional Ecological Knowledge for Cloud Forest Ecosystem Restoration in Ecuador

The importance of forests for biodiversity conservation has been well recognized by the global community; as a result, conservation efforts have increased over the past two decades. In Ecuador, the lack of integrated information for defining and assessing the status of local ecosystems is a major challenge for designing conservation and restoration plans. Thus, the objectives of this study were (1) to examine the regeneration status of cloud forest remnants, some of which had experienced past human disturbance events, (2) to explore a local rural community’s traditional ecological knowledge (TEK) relevant for restoration and (3) to investigate the integration between TEK and ecological science-based approaches. A survey of regeneration status was conducted in four remnants of cloud forests (n = 16) in Cosanga, Napo Province, in the Andes of northeastern Ecuador. The species of young trees (0.5–5 m height) were identified over 0.16 ha. In-depth interviews of individuals from local communities (n = 48) were conducted to identify socio-ecologically important native species. The results showed significant differences (p < 0.001) in species richness and the stem density of seedlings and saplings in gaps. The stem density of Chusquea sp., a bamboo species, explained 63% of the variation in species richness and 48% of the variation in the abundance of seedlings and saplings between plots. Informants cited 32 socio-ecologically important species, of which 26 species were cited as sources of food and habitats for wildlife. The ranking of species based on a relative importance index and a cultural value index—taking into account both the spread of knowledge among local informants and the multiplicity of uses—revealed that Hyeromina duquei, Citharexylum montanum, Eugenia crassimarginata and Sapium contortum were traditionally the most valuable species for both humans and wildlife. Informants also recommended 27 species for future planting, of which 19 species were amongst the rarest species in the regeneration survey. In conclusion, the results demonstrate a synergy between TEK and ecological science-based approaches (regeneration survey) to natural ecosystem research. Thus, traditional ecological knowledge can provide insights into ecosystem–plant–animal interaction, and to identify native species useful for both humans and wildlife for forest restoration projects to reconnect isolated cloud forest fragments.

Vascular epiphytes in the cloud forests of the Serra da Mantiqueira, Southeastern Region of Brazil

Abstract Vascular epiphytes represent a remarkable characteristic of the tropical cloud forests. The Serra da Mantiqueira (SM) represents one of the main highland areas of Brazil harboring vegetation remnants, and highlighting the cloud forests. We present a checklist of the vascular epiphytes found in the cloud forests of the SM, discussing the data about taxonomic representativity, distribution in the phytogeographic domains, habits, threatened status in Brazil and the states comprising the SM (Espírito Santo-ES, Minas Gerais-MG, Rio de Janeiro-RJ, São Paulo-SP). Field expeditions were performed between 2012 and 2019, as well as data gathering from scientific collections and published articles. We found 678 species, representing approximately 20% and 30% of the species found in Brazil and Atlantic forest, respectively. The richest families (Orchidaceae, 288 spp.; Bromeliaceae, 112 spp.; Polypodiaceae 65 spp.) corroborated the patterns found in different scales. Forty-one species are threatened nationally (and regionally, there are 149 in ES, 55 in MG, six in RJ, 31 in SP). These numbers of richness and threatened species highlight the relevance of directing efforts toward knowledge and conservation of both cloud forest remnants and SM as a whole, under pain of losing of a large part of the floristic diversity of Atlantic forest.

Diversity snapshot of green–gray space ants in two Mexican cities

This study evaluates changes in the diversity and composition of ants that inhabit contrasting environmental conditions (green and gray spaces) in two cities of different size and degree of urbanization: Xalapa and Coatepec (Veracruz, Mexico), both of which are surrounded by cloud forest remnants, croplands and pastures. In each city, a green space and a gray space of similar area were selected (~ 31 ha) and ten sampling sites were randomly placed within each environment. Tuna in oil and honey were used as baits to collect soil ants, entomological nets to capture vegetation ants and Winkler sacks for leaf-litter ants. Ant species richness (0D) and diversity (1D) was greater in Coatepec (the smaller and less urbanized city) than in Xalapa. However, the pattern observed when comparing green and gray spaces differed between the cities: the greatest diversity (0D and 1D) was observed in the gray space of Coatepec and the lowest diversity in the green space of Xalapa. In both cities, the similarity of species composition between habitat conditions was close to 50% and the comparison of green spaces between the cities showed that these are more different to each other than is the case with the gray spaces. These results suggest that the characteristics of each city influence the ant diversity contained in green and gray spaces differently and can promote differentiation in species composition within the same city.

The surrounding landscape influences the diversity of leaf-litter ants in riparian cloud forest remnants.

Riparian vegetation is a distinctive and ecologically important element of landscapes worldwide. However, the relative influence of the surrounding landscape on the conservation of the biodiversity of riparian remnants in human-modified tropical landscapes is poorly understood. We studied the surrounding landscape to evaluate its influence on leaf-litter-ant alpha and beta diversity in riparian remnants in the tropical montane cloud forest region of central Veracruz, Mexico. Sampling was carried out in 12 sites with riparian vegetation during both rainy (2011) and dry (2012) seasons. Ten leaf-litter samples were collected along a 100-m transect per site and processed with Berlese-Tullgren funnels and Winkler sacks. Using remotely-sensed and ground-collected data, we characterized the landscape around each site according to nine land cover types and computed metrics of landscape composition and configuration. We collected a total of 8,684 ant individuals belonging to 53 species, 22 genera, 11 tribes, and 7 subfamilies. Species richness and the diversity of Shannon and Simpson increased significantly in remnants immersed in landscapes with a high percentage of riparian land cover and a low percentage of land covers with areas reforested with Pinus, cattle pastures, and human settlements and infrastructure. The composition of ant assemblages was a function of the percentage of riparian land cover in the landscape. This study found evidence that leaf-litter ants, a highly specialized guild of arthropods, are mainly impacted by landscape composition and the configuration of the focal remnant. Maintaining or improving the surrounding landscape quality of riparian vegetation remnants can stimulate the movement of biodiversity among forest and riparian remnants and foster the provision of ecosystem services by these ecosystems. Effective outcomes may be achieved by considering scientific knowledge during the early stages of riparian policy formulation, in addition to integrating riparian management strategies with broader environmental planning instruments.

Plastic sheets: a new method for collecting faecal samples with seeds dispersed by birds

Abstract:For birds, we tested the efficacy of a technique used to obtain faecal samples and their seed content from bats by placing plastic sheets below mist nets. This method was compared with that of collecting faecal samples using cotton bags. Plastic sheets were placed below each of eight mist nets to obtain faecal samples from birds caught in cloud forest remnants. Each bird was then placed separately in a cotton bag to catch any other seeds excreted. There were 84 faecal samples in total: 64 with no seeds and 20 with seeds; of the latter 65% were obtained from the plastic sheets. A total of 407 seeds were collected, 317 from 11 plant species were collected on the plastic sheets and 90 belonging to six plant species in the bags. Seed richness and abundance were significantly greater for samples obtained using the plastic sheets than with the cotton bags. Although the number of bird faecal samples obtained did not differ between methods (13 vs 7), with the plastic sheets the number of faecal samples with seeds increased. Thus, to obtain more representative faecal samples from frugivorous birds, we strongly recommend the use of plastic sheets as part of the technique.

Applications de méthodologies participatives pour l'analyse du déboisement en forêt tropicale de montagne à San Luis Potosí, Mexique

Les forêts tropicales de montagne, ou forêts de brume, sont parmi les écosystèmes les plus riches en biodiversité de la planète. L'État de San Luis Potosí au Mexique a perdu 2 868 hectares de ces forêts en 35 ans. Cet article analyse, dans ce contexte, les causes de ce déboisement et les solutions possibles pour protéger les derniers lambeaux de ces forêts de brume en s'appuyant sur des techniques de recherche participatives : ateliers, cartographie participative, transects, entretiens semi-structurés et observations participatives. Les premières causes de destruction de ces forêts sont les contrats d'exploitation forestière, les subventions publiques à l'élevage, le défrichage pour les cultures et l'abattage sélectif. Si les services écosystémiques rendus par les forêts tropicales de montagne sont bien connus, ils sont moins appréciés que les services rendus par l'agriculture et l'élevage. De plus, les effets du sous-développement, de la pauvreté et des problèmes liés à la propriété foncière se conjuguent au détriment de cet écosystème, qui risque de disparaître dans les prochaines années. Cette étude fait valoir enfin que la création de réserves forestières communautaires représenterait la seule solution réaliste permettant de conserver cet écosystème en voie de disparition.

Population genetics of the East African White-eye species complex

The Eastern Afromontane biodiversity hotspot consists of isolated mountain massifs embedded within the dry lowland savannas of East Africa and of which the peaks and ridges are covered by cloud forest remnants. These cloud forests are home to the Mountain White-eye (Zosterops poliogaster), while three congeneric species (Abyssinian White-eye, Zosterops abyssinicus; Yellow White-eye, Zosterops senegalensis; Pemba White-eye, Zosterops vaughani) inhabit the adjacent lowland savannas. We sampled individuals of all four species across Kenya to analyse interspecific genetic relationships as well as intraspecific differentiation among mountain populations of Z. poliogaster. While the level of genetic differentiation among the four species was rather low, genetic differentiation within Z. poliogaster was very high, even between geographically neighbouring populations. Overall, levels of genetic variation varied strongly across all four species, with much higher diversity detected within the three lowland ones. The highland species was characterised by numerous private alleles that were geographically restricted at populations from single mountains, some of which showed evidence of recent population bottlenecks. We conclude that Z. poliogaster populations are both of high conservation value and conservation concern, given the high proportion of endemic alleles and the genetic signatures of high genetic drift and low gene flow that are typical for small and isolated populations.

Nectar secretion on fern fronds associated with lower levels of herbivore damage: field experiments with a widespread epiphyte of Mexican cloud forest remnants

The oldest group of plants in which nectar secretions have been observed are the Polypodiopsida (ferns sensu lato). Nectaries have been reported in a dozen extant genera. The function of these nectaries has been investigated in several fern species, and in some circumstances has been demonstrated to have an antiherbivore role, attracting and maintaining biotic defence (ants and/or other predatory arthropods). This study documents foliar nectaries in Pleopeltis crassinervata, a widespread Central American epiphyte growing on a variety of trees in cloud forest areas of Veracruz, Mexico. This is a new record for this genus and species. As previous experimental work on epiphytic species of Polypodium has demonstrated a protective role of ants for developing fronds, we conducted similar experiments (using nylon nail polish to cover nectaries rather than excluding ants with bands of sticky resin as in earlier work). The fronds of Pl. crassinervata developed over 6 weeks, at which time damage was assessed. The experiment was simultaneously conducted on a sympatric species lacking nectaries, Polypodium furfuraceum. Herbivore placement experiments were conducted with large and small caterpillars on both of these ferns. Fronds with nectaries covered suffered greater damage from herbivores over the course of their development, compared with fronds that had uncovered nectaries functioning normally. The parallel experiment on Po. furfuraceum showed no difference between manipulated and control fronds. Six species of ants (Brachymyrmex minutus, Crematogaster formosa, Paratrechina longicornis, Solenopsis geminata, S. picea and Wasmannia auropunctata) were observed visiting nectaries of Pl. crassinervata; most were effective in removing herbivore larvae placed on the fronds. The long evolutionary history of ferns may explain why some previous studies of fern nectaries have shown little or no benefit to ferns from nectary visitors, as any coevolved herbivores are those resistant to ant defence. The results suggest that ants protect Pl. crassinervata fronds against herbivory. The presence of nectaries, and the relationship with ants, may contribute to this fern's widespread occurrence and persistence in the face of disturbance, though many other factors also play a role. Ant defence may be more likely to benefit a widespread species of disturbed habitats that encounters a wide range of non-adapted herbivores.

First records of myxomycetes from El Salvador

Myxomycetes have been studied formally in most of Central America except for El Salvador. Even though this country is the last in the region to begin an official inventory for this group of organisms, the 37 new records reported herein suggest that the myxobiota of El Salvador can be valuable for biogeographical analyses. As an example, this study reports Perichaena tessellata for the first time in the Neotropical region. Such an observation along with studies conducted in previous years in Central America show that the Mesoamerican biodiversity hotspot can provide important information to understand myxomycete dynamics in tropical areas. Additionally to the latter, during the present study a first characterization of the species of myxomycetes present in Montecristo National Park was also carried out. This is an important contribution to the biological knowledge of critical conservation areas in Central America since such park is one of the few remnants of cloud forest in El Salvador. For microbial conservation purposes, these types of rapid biodiversity assessments are imperative in understudied areas of the world such as El Salvador and necessary in forest types such as Montecristo that are threatened by climate and land use change.

Passiflora unipetala, a New Bat-pollinated Species ofPassiflorasupersect.Tacsonia(Passifloraceae)

Passiflora unipetala P. Jorg., Muchhala & J. M. MacDougal (Passifloraceae) is described from two cloud forest remnants in Pichincha, Ecuador, and is assigned to the Andean endemic Passiflora L. supersect. Tacsonia (Juss.) Feuillet & J. M. MacDougal. This new species with yellowish green flowers is distinguished from all other passionflowers by having only one petal. It is pollinated by bats, which is rare in Passiflora.

Human access and landscape structure effects on Andean forest bird richness

We analyzed the influence of human access and landscape structure on forest bird species richness in a fragmented landscape of the Colombian Andes. In Latin America, habitat loss and fragmentation are considered as the greatest threats to biodiversity because a large number of countryside villagers complement their food and incomes with the extraction of forest resources. Anthropogenic actions may also affect forest species by bird hunting or indirectly through modifying the structure of forest habitats. We surveyed 14 secondary cloud forest remnants to generate bird species richness data for each of them. We also quantified six landscape structure descriptors of forest patch size (patch area and core area), shape (perimeter of each fragment and the Patton’s shape index) and isolation (nearest neighbor distance and edge contrast), and generated (using principal components analysis) a synthetic human influence variable based on the distance of each fragment to roads and villages, as well as the total slope of the fragments. Species richness was related to these variables using generalized linear models (GLMs) complemented with model selection techniques based on information theory and partial regression analysis. We found that forest patch size and accessibility were key drivers of bird richness, which increased toward largest patches, but decreased in those more accessible to humans and their potential disturbances. Both patch area and human access effects on forest bird species richness were complementary and similar in magnitude. Our results provide a basis for biodiversity conservation plans and initiatives of Andean forest diversity.

Composición florística de un bosque mesófilo del centro de Veracruz, México

En la región centro de Veracruz existen fragmentos de bosque mesófilo de montaña (BMM) que no se han explorado. Nosotros estudiamos la composición florística y algunos aspectos de la estructura de un BMM en la localidad de La Cortadura. El muestreo de leñosas, herbáceas y epífitas vasculares se realizó en tres microcuencas (1000 m2 cada una). Las áreas muestreadas tuvieron gran cobertura con árboles de buena altu ra, algunos emergentes, y la proporción de formas de vida fue igual entre microcuencas. Se registraron 258 especies ( 150 géneros, 82 familias), pero el bosque en su interior es heterogéneo. Aunque el número de especies en cada microcuenca fue parecido (144- 163), las tres microcuencas sólo compartieron 55 especies (34-38%). El BMM de La Cortadura está muy bien conservado, tiene 58 y 31 o/o de las familias que habitan preferentemente o exclusivas en este tipo de vegetación, y se han encontrado nuevos registros de distribución y una nueva especie.

Illegal logging, landscape structure and the variation of tree species richness across North Andean forest remnants

We explored the influence of a common practice in tropical countries, namely illegal logging for household consumption (ILHC), as well as that of characteristics of habitat structure on the variation of tree species richness across 10 cloud forest remnants of a Colombian Andean landscape. We estimated species richness for total, early and late successional tree species for each forest fragment. We also generated a binomial ILHC variable and six quantitative habitat descriptors related to patch size, shape and isolation. The data were analyzed with generalized linear models (GLMs) and model selection techniques based on Information Theory, complemented with partial regression analyses. We found that the presence of ILHC decreased the number of species for all tree groups, being this variable the major driver of richness variation across forest remnants. Our analyses also indicated that landscape characteristics played secondary roles in determining tree richness in all cases. Additionally, stronger negative impacts of ILHC on late successional tree species suggest that these logging activities are likely to move back ecological succession towards earlier stages of this process. As far as we know, this is the first study documenting the relative importance of ILHC practices against landscape structure for tree species richness. Our results strongly emphasize the need to consider ILHC in investigations and conservation initiatives involving tree species richness in fragmented tropical landscapes.

Mistletoe infection of trees located at fragmented forest edges in the cloud forests of Central Veracruz, Mexico

We investigated the Psittacanthus schiedeanus mistletoe infection of its preferred host tree species Liquidambar styraciflua in remnants of cloud forest in Central Veracruz, Mexico. We studied whether or not the location of host trees on forest fragment edges has a direct effect on mistletoe infection, and explored among host tree variation in intensity of infection. In four 1 ha plots, we marked 200 L. styraciflua and recorded height, diameter at breast height (DBH), distance to fragment edge, distance to conspecific tree, and number of mistletoe adult plants per tree, or canopy area (upper or medium-low). Overall, tree densities varied among plots, but not the number of infected or non-infected L. styraciflua trees. Fifty-nine percent (118/200) of the L. styraciflua trees were infected. They were similar in the number of P. schiedeanus plants per tree, but not in height, DBH, or distance to conspecifics. The most severely infected trees were tall, located on fragment edges, and located near an infected conspecific. Trees located on fragment edges had more mistletoe plants per tree and medium-low area of the tree. Also individual tree features as height and distance to conspecific affected, but not DBH. We suggest that individual differences among host trees play an important role in explaining local abundance and distribution of mistletoe plants. Inside forest fragments, tree density of Liquidambar, and edges lengths are important factors in determining the presence and intensity of P. schiedeanus infection.

Seed Dispersal of the Mistletoe Psittacanthus schiedeanus by Birds in Central Veracruz, Mexico1

ABSTRACTMistletoes are hemiparasitic plants that frequently depend on frugivores for seed dispersal; yet their seed dispersal ecology is still poorly known. The mistletoe Psittacanthus schiedeanus (Loranthaceae) was studied for a five‐month period in cloud forest remnants in central Veracruz, Mexico, to determine its seed dispersal ecology. We hypothesized that dispersal ecology of this mistletoe species is directly affected by the fruit‐eating bird abundance, and asked if this species is following the high‐investment strategy as suggested by Godschalk (1983). To evaluate this, we determined the morphological and nutritional characteristics of mistletoe fruit, the availability of ripe fruits along the mistletoe fruiting phenology, and the abundance of fruit‐eating birds. Because P. schiedeanus is dispersed by generalist rather than specialist birds, we asked if this mistletoe species is ripening fruits during the fruit scarcity time (with highest possibilities of being consumed and dispersed by birds). We compared P. schiedeanus ripe fruit production to the cloud forest tree leaf fall and fruit production. Psittacanthus schiedeanus matures its nutritious fruits from November to April, with a peak of abundance in January and February. We found a synchrony between the abundance of P. schiedeanus ripe fruits and the abundance of Gray Silky‐flycatchers (Ptilogonys cinereus) and Social Flycatchers (Myiozetetes similis); however, this was not the case with Cedar Waxwings (Bombycilla cedrorum), although these birds play an important role in the mistletoe dispersal. The fruiting pattern of P. schiedeanus, together with the fact that it is an important food resource for generalist rather than specialist frugivorous birds, suggest that this mistletoe is using the nutrient investment strategy to attract dispersers during a time of fruit scarcity.RESUMESLos muérdagos son plantas hemiparasitas que a menudo dependen de las aves frugivoras para dispersar sus semillas; sin embargo, sus estrategias de dispersión son poco conocidas. El muérdago Psittacanthus schiedeanus (Loranthaceae) se estudió durante cinco meses en un remanente de bosque mesófilo de montaña en el centre de Veracruz, México, para determinar la ecologyía de dispersión de sus semillas por las aves. Presumimos que la ecologia de dispersión de este muérdago está relacionada directamente con la abundancia de las aves frugívoras; y nos preguntamos si esta especie sigue la estrategia de alta inversión en nutrimentos sugerida por Godschalk (1983). Para evaluar esto, determinamos las características morfológicas y nutritivas de los frutos del muérdago, la disponibilidad de frutos maduros a lo largo de su fenología de maduración de frutos y la abundancia de las aves frugívoras. Debido a que P. schiedeanus es dispersado por aves generalistas, nos preguntamos si los frutos de este muérdago maduran cuando hay escasez de otros frutos. Comparamos la producción de frutos maduros de P schiedeanus con la caída de las hojas y la producción de frutos en los árboles de bosque mesófilo de montaña. Psittacanthus schiedeanus madura sus frutos nutritivos de no‐viembre a abril, con un pico de abundancia en enero y febrero. Durante el periodo de estudio, encontramos sincronía entre la abundancia de frutos maduros de P. schiedeanus y la abundancia de las aves Ptilogonys cinereus j Myiozetetes similis; sin embargo, este no fue el caso con Bombycilla cedrorum, a pesar del papel importante que estas aves juegan en la dispersión de este muérdago. El partón de fructificación de P, schiedeanus, aunado a que es un recurso alimentario importante para aves generalistas, en lugar de especialistas, sugiere que este muérdago está utilizando una estrategia de alta inversión en nutrimentos para atraer dispersores durante el tiempo de escasez de frutos.

Seed Dispersal of the Mistletoe Psittacanthus schiedeanus by Birds in Central Veracruz, Mexico1

Mistletoes are hemiparasitic plants that frequently depend on frugivores for seed dispersal; yet their seed dispersal ecology is still poorly known. The mistletoe Psittacanthus schiedeanus (Loranthaceae) was studied for a five-month period in cloud forest remnants in central Veracruz, Mexico, to determine its seed dispersal ecology. We hypothesized that dispersal ecology of this mistletoe species is directly affected by the fruit-eating bird abundance, and asked if this species is following the high-investment strategy as suggested by Godschalk (1983). To evaluate this, we determined the morphological and nutritional characteristics of mistletoe fruit, the availability of ripe fruits along the mistletoe fruiting phenology, and the abundance of fruit-eating birds. Because P. schiedeanus is dispersed by generalist rather than specialist birds, we asked if this mistletoe species is ripening fruits during the fruit scarcity time (with highest possibilities of being consumed and dispersed by birds). We compared P. schiedeanus ripe fruit production to the cloud forest tree leaf fall and fruit production. Psittacanthus schiedeanus matures its nutritious fruits from November to April, with a peak of abundance in January and February. We found a synchrony between the abundance of P. schiedeanus ripe fruits and the abundance of Gray Silky-flycatchers (Ptilogonys cinereus) and Social Flycatchers (Myiozetetes similis); however, this was not the case with Cedar Waxwings (Bombycilla cedrorum), although these birds play an important role in the mistletoe dispersal. The fruiting pattern of P. schiedeanus, together with the fact that it is an important food resource for generalist rather than specialist frugivorous birds, suggest that this mistletoe is using the nutrient investment strategy to attract dispersers during a time of fruit scarcity.

Frugivorous birds, host selection and the mistletoe Psittacanthus schiedeanus, in central Veracruz, Mexico

Frugivorous birds play an important role in parasitic mistletoe transmission among host species. The foraging behaviour and host selection of Psittacanthus schiedeanus mistletoe fruit-eating birds was studied in cloud forest remnants in Central Veracruz, México. Cedar waxwings, Bombycilla cedrorum, gray silky-flycatchers, Ptilogonys cinereus, and social flycatchers, Myiozetetes similis, eating ripe whole mistletoe fruits and defecating or regurgitating the seeds were observed. That variation in host species selection by frugivorous birds had a direct effect on mistletoe dispersion was hypothesized. To test whether mistletoe host species are visited in proportion to their abundance (total number of trees), or infested-tree abundance (total number of infested trees), or abundance of mistletoes (total number of individual mistletoe plants in each host species), the number of trees, infested trees and individual mistletoe plants were recorded. Tree abundance, infested-tree abundance and mistletoe abundance were different among host species. Frequency of birds' visits to host species varied depending on the tree, infested-tree, or mistletoe abundance. Liquidambar styraciflua was the most abundant host species with the highest number of infested trees and individual mistletoe plants, but Persea americana and Crataegus mexicana host species had the highest number of individual mistletoe plants in each tree. Our data suggest that L. styraciflua was the most selected host species by the three frugivorous birds. Host selection by birds is one behavioural factor in explaining differences in prevalence among host species, and variation in infection levels among individuals of one host species.RESUMEN. Las aves frugívoras juegan un importante papel en la transmisión de muérdagos parásitos hacia sus árboles hospederos. La conducta de forrajeo y selección de hospedero de aves consumidoras de frutos del muérdago Psittacanthus schiedeanus fueron estudiados en remanentes de bosque mesófilo de montaña del Centro de Veracruz, México. Bombycilla cedrorum, Ptilogonys cinereus and Myiozetetes similis fueron observados consumiendo frutos maduros enteros y defecando o regurgitando las semillas. Hipotetizamos que la variación en la selección de la especie hospedera por las aves frugívoras tiene un efecto directo en la dispersión del muérdago. Para probar si las especies de árboles hospederos son visitadas en proporción a su abundancia (número total de árboles), o la abundancia de hospederos infectados (número de árboles infectados) o la abundancia de muérdagos (número total de plantas individuales de muérdago en una sola especie de árbol); el número de árboles, árboles infestados y plantas de muérdago fueron registradas. La abundancia de árboles, de árboles infestados y de plantas de muérdago fue diferente entre las especies de árboles estudiadas. La frecuencia de visitas de las aves a las especies hospederas varió de acuerdo a la abundancia de árboles, de árboles infestados y de plantas de muérdago. Liquidambar styraciflua fue la especie hospedera más abundante con el mayor número de árboles infestados y abundancia de muérdagos, pero las especies Persea americana y Crataegus mexicana presentaron el mayor número de plantas de múerdago por árbol. Nuestros datos sugieren que L. styraciflua fue la especie hospedera más seleccionada por las aves frugívoras. La selección de hospederos por las aves es uno de los factores conductuales que explican las diferencias en prevalencia entre especies de hospedero, y la variación en los niveles de infestación entre individuos de una de las especies de hospedero.