Dung beetles from two sustainable-use protected forests in the Brazilian Amazon

Abstract Background The Amazon Forest is one of the world's most biodiverse ecosystems and yet its protected areas are understudied concerning insects and other invertebrates. These organisms are essential for tropical forests due to their ecological processes, with some species being very sensitive to habitat disturbances. Dung beetles (Coleoptera, Scarabaeidae, Scarabaeinae) have been used as bioindicators for more than 30 years and were surveyed to assess the insect biodiversity of two sustainable-use forest reserves in the Brazilian Amazon. New information We report inventories of dung beetles from two Amazonian forest reserves in Pará State, Brazil: the Tapajós National Forest and the Carajás National Forest. Surveys were carried out with baited-pitfall traps installed in 2010, 2016, 2017 and 2019. We collected a total of 3,772 individuals from 19 genera and 96 species. We highlight the importance of Amazonian protected areas as refugia for insect biodiversity, particularly dung beetles, which contribute to many key ecosystem processes.


Background
The Amazon Forest is one of the world's most biodiverse ecosystems and yet its protected areas are understudied concerning insects and other invertebrates.These organisms are essential for tropical forests due to their ecological processes, with some species being very sensitive to habitat disturbances.Dung beetles (Coleoptera, Scarabaeidae, Scarabaeinae) have been used as bioindicators for more than 30 years and were surveyed to assess the insect biodiversity of two sustainable-use forest reserves in the Brazilian Amazon.

Introduction
The Amazon Forest has global importance for biodiversity, being amongst the world's most diverse tropical ecosystems (Barlow 2018).The region's warm and humid climate makes Amazonian forests a unique ecosystem with extraordinary biodiversity levels, particularly for insects (Fearnside 2008, Sobral-Souza andLima-Ribeiro 2017).
With the human footprint and climate extremes increasing within tropical regions (França et al. 2020a), protected areas are increasingly becoming the final refuges for biodiversity, including many restricted-range and highly threatened species (Rylands andBrandon 2005 , Sollmann et al. 2008).Until 2009, around 54% of the remaining Amazon Forest in Brazil was part of a protected area network, ranging from strictly protected areas and indigenous lands to sustainable use forests (Soares-Filho et al. 2010).The importance of these protected areas goes beyond biodiversity conservation by sustaining local livelihoods (Naughton-Treves et al. 2005, Spinola et al. 2020), preventing climate-tipping points (Walker et al. 2009) and supporting the mitigation of climate changes through carbon accumulation and reduction of Greenhouse Gases (GHG) emissions from deforestation (Soares-Filho et al. 2010, Walker et al. 2020).
Despite the unparalleled contribution of insects to the totality of biodiversity (Zhang 2011) and their important role in many critical ecological functions (Nichols et al. 2008, Campbell et al. 2012, Dangles and Casas 2019), insects are understudied when compared to vertebrates (Dornelas and Daskalova 2020).For example, only 1.67% of the known invertebrate species have been assessed by the IUCN Red List of threatened species compared with 68.9% of all vertebrates (Kitching et al. 2020).The lack of studies with insects and invertebrates is also evidenced within Amazonian protected areas.
Here, we: (1) present a list of dung beetle species surveyed at two sustainable-use protected forests in the Brazilian Amazon -the Tapajós National Forest and the Carajás National Forest (FLONAS); and (2) discuss insights associated with the species distribution and previous recordings in literature.

Study region
The Tapajós National Forest and Carajás National Forest (hereafter 'Tapajós' and 'Carajás', respectively) cover 527,319 ha and 411,948 ha of Amazonian forests, respectively, spread across multiple municipalities in the State of Pará, Brazil (Fig. 1).These FLONAS are located in two Amazonian biogeographical regions with distinct socio-environmental contexts.Specifically, the Tapajós region has a more recent history of agriculture expansion and lower deforestation rates than the Carajás region (Braz 2016), with FLONA Carajás located within a mosaic of federal and state forest reserves, national parks and indigenous protected lands (Piló et al. 2015).The climate is characterised as hot-humid (Köppen's classification) and the annual average temperature is 25-26°C in both regions, which have short dry seasons in August-November (average precipitation [mm]: Tapajós = 1405.8)and July-September (Xingu = 84.8).Surveyed sites are within the 'terra-firm' forests, with vegetation varying depending on soil and relief.

Sampling design
Dung beetles were sampled within a total of 13 forest sites (Carajás = 3 and Tapajós = 10).We surveyed Carajás in February-March 2019, while Tapajós forests were surveyed in June-July 2010, June-July 2016, March-April 2017 and Feb-March 2019.These field sites are part of the Long-Term Ecological Research Program of the Sustainable Amazon Network (PELD-RAS).At each of our forest sites, dung beetles were sampled at three sampling points (0, 150 and 300 m) along a 300-m transect.As in França et al. (2020b), we used three dung-baited pitfall traps arranged at the ends of a 2-m equilateral triangle at each sampling point, resulting in a total of 117 traps (21 and 96 pitfalls in Carajás and Tapajós, respectively).Pitfall traps were 1-litre plastic containers (14 cm in diameter; 9 cm deep) buried in the ground with the opening at ground level and protected from rain with a plastic lid suspended 15 cm above the surface.Each trap was part-filled with a saline killing solution, had a bait container with 35 g of dung (4:1 pig to human ratio, following Marsh et al. (2013)) supported by a wire above the trap and was left in the field for 48 hours.

Data resources
All trapped dung beetles were collected and taken to the laboratory, where they were sorted, mounted and identified to species (using identification key or descriptions) or morphospecies.Voucher specimens were deposited at the Entomological Section of the Zoological Collection (CEMT) at the Federal University of Mato Grosso, Brazil (UFMT).Specimens were photographed using the Leica M250C Photomontage Equipment (UFMT/ Finep) and an Olympus SZX16 stereomicroscope with expandable stream motion imaging software v. 2.5 (UoB/Liv Sidse Hansen Foundation).The morphospecies identification numbers are not indicating the amount of species collected at the sites and are purely reference numbers for species across multiple projects.List and abundance of species present in FLONA Tapajós and

Carajás
Subfamily Scarabaeinae Latreille, 1802 Notes: We collected 3,772 dung beetles from 96 species and 19 genera.Only 14 of the 96 identified species were found in both FLONAS (Table 1).Canthidium deyrollei was the most abundant species, with exclusive records from FLONA Tapajós.The three most diverse genera comprise distinct functional strategies in dung beetles: Eurysternus (endocoprids -i.e.residents in the dung resource); Dichotomius (paracoprids -i.e.tunnellers, where all species mostly dig tunnels close to or immediately below the resource) and Canthon (telecoprids -i.e.rollers), which could be an indicator of whole exploitation of dung resources in Amazonian forests.However, if abundance is considered, small paracoprids (especially Onthophagus species) were the most abundant functional group, which is expected for the Amazon Region (FVM, pers.obs).We discuss below the current knowledge about the distribution and ecology of each identified genera.Table 1.
List and abundance of species present in FLONA Tapajós and Carajás.
Dung beetles from two sustainable-use protected forests in the Brazilian ...
The specimens were identified from comparison with the original types and descriptions, which were analysed by one of the authors.Two species were identified to the species level in our survey in FLONA Tapajós: Canthidium deyrollei Harold, 1867 and C. melanocephalum (Olivier, 1789) (Fig. 2H-I).Other 22 species are present, but could not be identified.Dung beetles from two sustainable-use protected forests in the Brazilian ...

Genus Canthon Hoffmannsegg, 1817
Notes: This is also a very diverse genus, comprising more than 170 described species (Halffter and Martinez 1977).Most species are considered copro-necrophagous, although some exhibit predatory behaviour -for example, hunting ants (Halffter and Matthews 1966) -or use dead insects and millipedes (Villalobos et al. 1988, Silva et al. 2014), rotten fruits and fungus as food resources (Vaz-de-Mello 1999).This genus is endemic to the Americas and its distribution ranges from the USA to Uruguay and northern Argentina.Recent revisions have been made for some Canthon subgenera (Nunes et al. 2018, Nunes et al. 2020).Typically, these species are abundant in lowland forest environments, with individuals found perching on leaves exposed to light (Nunes et al. 2018)

Genus Cryptocanthon Balthasar, 1942
Notes: This genus comprises around 43 species occurring from Brazil to Mexico (Arias and Medina 2014, Martínez-Revelo et al. 2020, Giraldo-Mendonza 2022).The only available information about their habitat describes specimens inhabiting the leaf litter of humid and tropical forests, both in mountains and low altitudes (Cook 2002).For the identification of the species, the following works were mainly used: Cook (2002).
Cryptocanthon campbellorum Howden, 1973 (Fig. 3D) was the only species, which is usually collected in leaf litter, with flight interception and pitfall traps baited with human faeces (Cook 2002).

Genus Dichotomius Hope, 1838
Notes: According to the most recent taxonomic revision from one of the subgenera of Dichotomius, this Neotropical genus comprises around 190 species widely distributed from the USA to Argentina (Nunes and Vaz-de-Mello 2019).The four subgenera are either being revised or were recently revised (Nunes et al. 2016, Valois et al. 2017, Maldaner et al. 2018, Nunes and Vaz-de-Mello 2019).Dichotomius species occur in all Brazilian biomes and can be collected in pastures, savannahs or forests.The genus as a whole is considered paracoprid -i.e.tunnellers (Nunes and Vaz-de-Mello 2019).For the identification of the species, the following works were mainly used: Nunes et al. ( 2016), Valois et al. (2017), Maldaner et al. (2018), Nunes and Vaz-de-Mello (2019).

Genus Eutrichilum Martínez, 1969
Notes: This genus presents a group of species that inhabit South American lowlands, east of the Andes as far south as Buenos Aires in Argentina; one species in Costa Rica (Vaz-De-Mello 2008).Species of this genus are frequently necrophagous and are often attracted to light (Vaz-De-Mello 2008).Eutrichillum sp. 1 was the only species recorded within the Tapajós region.

Genus Hansreia Halffter & Martínez, 1977
Notes: This is an Amazonian genus with six species distributed across Brazil, French Guiana and Venezuela (Halffter and Martinez 1977); recently revised by Valois et al. (2015).Valois et al. (2015) was used for species identification.There is not much ecological information about Hansreia dung beetles ( Hadara et al. 2020).Only the species Hansreia oxygona (Perty, 1830) was recorded within the Carajás region (Fig. 4L).Dung beetles from two sustainable-use protected forests in the Brazilian ...

Genus Isocopris Pereira e Martínez, 1960
Notes: This Neotropical genus, frequently misidentified as Dichotomius, comprises seven known species recently revised by Rossini and Vaz-de-Mello (2017), the same work being used to identify the species.No biological information for the genus was found.Two species were identified in our study: Isocopris imitator (Felsche, 1901) and I. nitidus (Luederwaldt, 1922) (Fig. 4M-N).

Genus Ontherus Erichson, 1847
Notes: Occurring from Argentina to Mexico, this genus has approximately 60 species (Génier 1996, Génier 1998).Although most species are considered coprophagous or saprophagous, some complex associations with ants have been previously recorded (Génier 1996).For the identification of the species, the following works were mainly used: Génier (1996).One species was found in the Tapajós region: Ontherus carinifrons Luederwaldt, 1930 (Fig. 4O).This species belongs to a group called appendiculatus, which is widely distributed in South America (Génier 1996).Species from this group are usually collected in human or cattle dung, also using flight or light traps in sandy habitats (Génier 1996).

Genus Onthophagus Latreille, 1802
Notes: Considered a megadiverse and cosmopolitan genus with approximately 2,000 described species (Tarasov and Kabakov 2010).Some species have been recently revised (Rossini et al. 2018a, Rossini et al. 2018b), while others are under current revision.The species mentioned here have been recorded mainly in primary and secondary forests, through the use of both flight interception traps and pitfalls baited with dung or carrion (Korasaki et al. 2012).For the identification of the species, the following works were mainly used: Rossini et al. (2018a), Rossini et al. (2018b).Four species were identified in our study: Onthophagus digitifer Boucomont, 1932, O. gp. rubrescens, O. onthochromus Arrow, 1913and O. osculatii Guérin-Méneville, 1855 (Fig. 5A).

Genus Oxysternon Castelnau, 1840
Notes: This Neotropical genus comprises 11 species according to the last taxonomic revision by Edmonds and Zídek (2004) which was used for species identification.
Oxysternon beetles are usually found in primary and secondary forests (Gigliotti et al. 2011).The literature on the biology of the genus is scarce, but most species are considered as coprophagous and inhabit moist forests (Edmonds and Zídek 2004).Two species were recorded in this study: Oxysternon macleayi Nevinson, 1892 and O. silenus Castelnau, 1840 (Fig. 5B-C).

Genus Scybalocanthon Martínez, 1948
Notes: Scybalocanthon is a widespread genus occurring in South and Central America (Pereira andMartínez 1956, Silva andValois 2019).The genus comprises 24 valid species, most of which are diurnal and inhabit either moist or dry forests in the Amazon Region, Atlantic Rainforest and the Yungas (Silva andValois 2019, Silva andGénier 2019).Only the species Scybalocanthon sp. 1 was reported to the Carajás region.
Dung beetles from two sustainable-use protected forests in the Brazilian ...

Genus Uroxys Westwood, 1842
Notes: Uroxys is an exclusively Neotropical genus with more than 50 described species (Vaz-De-Mello 2008, Korasaki et al. 2012).This genus has species that can be found in grasslands and within primary and secondary forests; it also includes species specialised in sloth (Bradypodidae) dung (Korasaki et al. 2012).Uroxys cf.minutus was the only species reported in this study.

Discussion
The knowledge of biodiversity is key to providing information for conservation and management strategies, particularly within the hyperdiverse tropics (Barlow 2018).Our dung beetle surveys within FLONA Tapajós and Carajás highlight the importance of Amazonian Sustainable-Use protected forests for conserving insect biodiversity in the tropics.Protected areas have a key role as a thermal buffer against climate changes (Xu et al. 2022) and for the long-term maintenance of Amazonian biodiversity (Laurance 2005).However, Brazilian protected forests are largely underfunded, particularly in Amazonia (Silva et al. 2021) -which hinders their efficacy in protecting biodiversity and raises the urgency for new policies and funding mechanisms to enhance their efficacy.

Figure 1 .
Figure 1.Map showing the localities of Tapajós National Forest (FLONA Tapajós) and Carajás National Forest (FLONA Carajás; both in dark grey) in Pará State (medium grey), in the north of Brazil (light grey).
Dung beetles from two sustainable-use protected forests in the Brazilian ...