Hymenoptera Specimens from the Caño Negro Wetland, of the National Museum Collection, Costa Rica

Species List

To establish a reference baseline, a thorough search of the MNCR’s database was conducted to extract a list of Hymenoptera taxa originating from the Caño Negro Wetland, it can be accessed by the following link: https:// biodiversidad.museocostarica.go.cr/ Taxonomic data from the GBIF database for the area was also extracted to generate a comparison illustrating the representation percentage of taxa in the heritage collection.

SINAC Permits

Several field expeditions were carried out during which specimens were collected using various methods including traps, Malaise traps, sweep nets, light screens, and scent traps. Collections were conducted under collection permit SINAC-SE-DE-R-0154-2025 and scientific passport: SINAC- SE-DE-LC-0042-2025 for the expeditions from October 27- 31.

The Relevance of Ants in Site Conservation

Ants, members of the family Formicidae, represent a taxonomically and functionally dominant component in most terrestrial ecosystems, particularly in tropical regions [8]. Their omnipresence and the intricate ecological interactions they establish make them organisms of fundamental interest for biodiversity conservation, primarily in the following aspects:

Ecosystem Engineers and Key Regulators

A prominent group in terms of ecological impact are leaf-cutter ants of the genera Atta and Acromyrmex. Species such as Atta cephalotes and Acromyrmex octospinosus are recognized as ecosystem engineers due to their capacity to significantly modify the physical and biological environment [8, 9]. Their foraging and nest-building activity profoundly influences:

Nutrient cycling: They transport vast quantities of plant biomass underground, where the decomposition of organic matter in their fungal garden chambers enriches the soil with plant-available nutrients [10].

Soil structure: The excavation of their complex nests alters soil hydrology, aeration, and granular composition [11].

Vegetation dynamics: They act as significant herbivores, affecting vegetation composition, distribution, and regeneration [12]. Their presence and the integrity of their colonies are, therefore, indicators of the health and functionality of tropical ecosystems.

Army ants (Eciton burchellii, Eciton dulcium, Labidus coecus, Neivamyrmex pilosus, Nomamyrmex esenbeckii, Nomamyrmex hartigii) are apex predators with cascading trophic impacts [13, 14]. Their massive foraging columns exert considerable predatory pressure on other invertebrates, and occasionally small vertebrates, regulating their populations. Furthermore, their activity influences the behavior of other species, such as birds that follow the columns to capture fleeing prey [15]. The need for large extents of intact habitat to sustain their colonies makes them sensitive indicators of forest quality and extent [16].

Critical Mutualisms and Habitat Specialists

Several ant species establish obligate mutualistic relationships with plants, being essential for the latter’s persistence. The genera Azteca and Pseudomyrmex are paradigmatic examples. Azteca species form well- documented mutualisms with trees of the genus Cecropia, defending their host plants from herbivores and competing vines in exchange for shelter (domatia) and food (Müllerian bodies and nectar) [17, 18]. Similarly, many Pseudomyrmex species are obligate mutualists of acacias and other myrmecophytic plants, offering protection against herbivores and competitors [19]. The presence of Myrmelachista sp. on the list is also relevant, as some species are known for creating “devil’s gardens” by eliminating competing vegetation around their host plants, favoring their growth [20]. The conservation of these ants is intrinsically linked to that of their mutualistic plants, forming a complex of co-dependent species: Minor fungus- growing ants (Apterostigma sp., Cyphomyrmex cornutus, Lachnomyrmex scrobiculatus, Sericomyrmex amabilis) are essential components of nutrient cycling in leaf litter and soil. Unlike Atta and Acromyrmex, many of these species are more specialized in their fungal cultivation substrates and the microhabitats they occupy [21]. Their sensitivity to changes in leaf litter humidity and composition makes them potential bioindicators of understory integrity [22].

Turtle ants (Cephalotes minutus, Cephalotes multispinosus, Cephalotes porrasi, Procryptocerus belti, Procryptocerus pictipes) are highly specialized arboreal ants, both in their flattened morphology and habits [23]. They inhabit bark crevices, decaying wood, and domatia, contributing to canopy biodiversity. Their presence often denotes mature and well-structured forests, as they depend on specific resources and microhabitats associated with dead wood and arboreal architecture [24].

The bullet ant (Paraponera clavata) is a formidable forest floor predator, but its relevance is not limited to its trophic role. Its participation in the seed dispersal for certain plants has been documented, contributing to forest regeneration [25, 26]. Its dependence on primary and undisturbed forests makes it a habitat quality indicator.

Functional Diversity and Specialization

Genera with high species diversity and varied ecological roles, such as Camponotus, Pheidole, Odontomachus, Gnamptogenys, Strumigenys, Pyramica, and Hypoponera, are crucial for biodiversity:

Pheidole is one of the most diverse ant genera globally, with species occupying niches as granivores, scavengers, and predators [27]. High Pheidole diversity in an ecosystem is an indicator of species richness and complexity of trophic interactions.

Odontomachus (trap-jaw ants) and Gnamptogenys (specialized predators) are important for controlling populations of other invertebrates [28, 29].

Strumigenys ludia and other Pyramica sp. are microscopic and highly specialized predators of microarthropods in leaf litter, fundamental for decomposition processes and soil community maintenance [30]. The richness and abundance of these groups reflect the health of the invertebrate community and ecosystem integrity.

Invasive Species and Threats to Biodiversity

Finally, conservation relevance lies not only in beneficial native species but also in those that pose a significant threat. Species such as Wasmannia auropunctata (electric ant or little fire ant) are considered among the 100 most damaging invasive species globally [31]. Its presence on the list is of extreme conservation concern. Wasmannia auropunctata aggressively displaces native ant species and other invertebrates, reduces arthropod diversity, affects fruit production in some crops, and can sting small vertebrates, drastically altering community structure and ecological processes [32, 33]. Although Solenopsis sp. includes native species, the mention of Solenopsis invicta (red imported fire ant) or other invasive Solenopsis species would also indicate a critical threat to native biodiversity [34]. The management and control of these invasive species are crucial for protecting ecosystems and biological diversity.

Melipona beecheii and Meliponiculture in the Caño Negro Biological Corridor

The presence of Melipona species, such as M. beecheii, in the region surrounding the Caño Negro Wetland underscores the importance of stingless bees for the pollination of native flora and local crops. Although M. beecheii is more associated with dry forests, the genus’s importance in pollinating humid forests and agroforestry systems near the wetland is undeniable. González et al. [35] point out that traditional meliponiculture in Costa Rica, including areas near natural reserves, is vital for the conservation of these bees, which face pressure from habitat loss due to agricultural expansion and agrochemical use in the areas adjacent to Caño Negro. The deforestation of riparian forests bordering the wetland reduces nesting sites and resource sources, compromising the viability of Melipona populations and, consequently, the resilience of pollination in this key ecosystem.

Euglossini (Euglossa & Eulaema) and Caño Negro Wetland Connectivity

Orchid bees are crucial pollinators in the humid tropical forests surrounding and comprising much of the Caño Negro ecosystem. Their ability to fly long distances, documented by Janzen [36], makes them essential “genetic connectors” for plants found dispersed or in habitat fragments. In a mosaic of wetlands, rivers, and forest patches like Caño Negro, these bees maintain the gene flow of vital plant species for the ecosystem’s structure, including lianas and trees with specialized flowers. Habitat degradation and loss of floral diversity in the wetland’s buffer zones directly threaten these intricate pollination networks, affecting not only orchids but also the overall health of the forest [37].

Trigona corvina and Resource Dynamics in Caño Negro

The genus Trigona, with species like Trigona corvina, is omnipresent and ecologically dominant in the Neotropics, including the Caño Negro Wetland. These stingless bees are known for their aggressive foraging strategies and their ability to monopolize nectar and pollen sources. In the rich environment of Caño Negro, where floral resources can fluctuate seasonally with water levels and mass flowering events, the presence of T. corvina significantly influences resource partitioning among the pollinator community [38]. Its dominance can displace smaller or less competitive bee species from abundant floral patches, thus shaping interactions and coexistence within the pollinator guild and potentially limiting effective pollination for some plants.

Centris Analis and Floral Specialization in the Wetland Margins

Bees of the genus Centris, such as Centris analis, are specialists in collecting floral oils, a vital resource for their reproduction. In the diverse habitats of Caño Negro’s margins, where plant species like Malpighiaceae exist, these bees play an irreplaceable role. The oils are not only a nutritive lipid source for larvae but are also used to line brood cells, protecting them from humidity and pathogens in a typically humid environment. Vinson, et al. [39] highlighted the specificity of this interaction. The conservation of Centris populations in Caño Negro is directly linked to the presence and health of their host oil-producing plants. The alteration of native flora along the wetland’s edges, either by drainage or invasive species, directly threatens this coevolved mutualism and, therefore, the reproduction of these key bees.

Nocturnal Pollination in the Canopy’s Gloom

The presence of Megalopta centralis in the Caño Negro

ecosystem reveals the sophistication of its pollination networks. This halictid bee is one of the few truly nocturnal bees, specialized in exploiting floral resources available during crepuscular and nocturnal hours. Its compound eyes, adapted for high light sensitivity, allow it to navigate and forage in the low light of the tropical understory [40]. In Caño Negro, M. centralis complements the activity of diurnal pollinators, ensuring the reproduction of plants that open their flowers at dusk, an ecological strategy to avoid diurnal competition. This temporal niche reduces pressure on resources and contributes to wetland resilience by expanding the pollination window, which is vital for maintaining the area’s high plant biodiversity.

Solitary Bees of Caño Negro

Unlike their social relatives, solitary bees constitute the vast majority of bee species and operate individually, with each female building and provisioning her own nest. In the Caño Negro Wetland, genera present in your list such as Megachile (leaf-cutter bees), Xylocopa (carpenter bees), Lasioglossum (sweat bees), and various species of Centris and Ptiloglossa play irreplaceable ecological roles.

These bees exhibit an impressive diversity of nesting strategies adapted to Caño Negro’s varied microhabitats. Xylocopa bees excavate galleries in dead or soft wood, common in flooded forest areas and river margins, efficiently pollinating plants with poricidal anthers via vibration (buzz pollination). Megachile nest in pre-existing cavities, using leaf or petal pieces to construct larval cells, being important pollinators of legumes. Many species of Lasioglossum, Exomalopsis, and Ptiloglossa nest in the ground, preferably in bare soils or with sparse vegetation, utilizing trail edges and forest clearings. The presence of Ptiloglossa eximia and P. mexicana suggests specialization in collecting pollen from plants like Malpighiaceae, often during crepuscular hours, complementing the work of other diurnal pollinators [41].

The importance of these solitary bees for Caño Negro’s ecological resilience lies in their pollination efficiency and their complementarity with social species. Their diversity ensures that a wide range of plants, from shrubs to canopy trees, are effectively pollinated. However, their nesting specificity makes them particularly vulnerable to habitat degradation. The removal of dead wood, soil alteration by surrounding agricultural activities, and pesticide use directly affect their populations by eliminating their nesting sites and food sources [42]. The conservation of landscape heterogeneity in Caño Negro, including patches of native vegetation and decaying wood, is crucial for maintaining the diversity and pollination services of these solitary bees.

Critical Information Gap on Hymenoptera

Despite being an internationally significant Ramsar Site and the crucial role of insects in trophic networks and pollination, a “critical gap” exists in the ecological information regarding Hymenoptera in Caño Negro. Current studies have disproportionately focused on charismatic vertebrates, leaving insects “systematically overlooked” in official assessments. This lack of current and comprehensive records (with most dating from 1992-1994) hinders a comprehensive understanding of wetland health and impedes the formulation of data-driven conservation strategies for this vital group.

Hymenoptera as Ecosystem Engineers and Pillars of the Trophic Network

The bees and ants of Caño Negro are not mere components but “fundamental” to the ecosystem’s structure and function. Bees act as irreplaceable pollinators (Meliponini, Euglossini, Centris, solitary bees), ensuring plant reproduction. Ants, for their part, are “ecosystem engineers” (e.g., Atta, Acromyrmex modifying soils and cycling nutrients), “apex predators” (e.g., Eciton regulating populations), and establish “critical mutualisms” with plants (e.g., Azteca, Pseudomyrmex). Their functional diversity is essential for wetland resilience.

Sensitive Bioindicators of Environmental Health and Anthropogenic Threats

Hymenoptera, along with other insects like Odonata, are “bioindicators of the environmental health” of the wetland. The presence and diversity of species such as fungus- growing ants (sensitive to leaf litter and humidity) or “turtle ants” (indicators of mature forests) reflect habitat integrity. Their vulnerability to “surrounding habitat fragmentation,” “agricultural eutrophication” from adjacent pineapple crops, and pesticide use demonstrates how the well-being of these insects is a direct thermometer of the “external anthropogenic pressures” impacting Caño Negro.

Extreme Vulnerability to Habitat Degradation and Microhabitat Loss

The specificity of Hymenoptera makes them particularly susceptible to environmental alteration. Solitary bees (Xylocopa, Megachile, Lasioglossum) depend on resources such as dead wood, pre-existing cavities, or specific soil types for nesting. Orchid bees (Euglossa, Eulaema) require habitat connectivity for their foraging flights. The “removal of dead wood” or “soil alteration” directly impacts these populations, highlighting the need to conserve “landscape heterogeneity” within and on the periphery of the wetland.

Critical Threat from Invasive Hymenoptera Species

The presence of invasive Hymenoptera represents a “conservation concern.” The case of Orasema costaricensis in Galápagos, though outside Caño Negro, illustrates the devastating potential of parasitoid species. More directly, the mention of species like Wasmannia auropunctata (electric ant) and potentially invasive Solenopsis species (fire ant) in the list of Hymenoptera found in Costa Rica, indicates an “extreme” threat. These species “aggressively displace” native species, “reduce arthropod diversity,” and “drastically alter community structure,” demanding rigorous “monitoring” and “management” in Caño Negro.