Platycyamus regnellii (Fabaceae), native to Brazil, is distributed from southern Bahia to Espírito Santo States, Goiás, Minas Gerais, Rio de Janeiro, Paraná, and São Paulo states, especially, in the altitude semi deciduous forests. This plant is used to recover degraded areas and their wood in civil construction and carpentry, in the treatment of fever, poor digestion, and inappetence. Also, as medicinal plant against diabetes (Cruz et al. 2022) and, for having showy flowers, in landscaping in parks and gardens. In addition, P. regnellii can be used in consortium with pastures in order to provide shade for cattle (e.g. thermal comfort) and improving the quality of the pasture (e.g. nutrient recycling) (Martins et al. 2008). However, the arthropodfauna of this plant is little studied with only Phenacoccus sp. (Hemiptera: Pseudococcidae) related as a potential pest (Gomes 2018).

Insects can damage different parts of the plant or its leaves (adaxial and abaxial faces). Knowledge of the preferred leaf face is important for pest control (Damascena et al. 2017), which is more difficult for those who live and feed on the abaxial. Sucking insects, in general, prefer abaxial leaf face due to it has softer tissue, thinner epidermis, and more prominent ribs (Damascena et al. 2017), besides of to greater protection against climatic factors (e.g. solar radiation) and natural enemies. On the other hand, arthropods may prefer the adaxial leaf face due to lower force applied to remain on this face (Salerno et al. 2018). Relationships between insects can be intra or interspecific, with or without prejudice to the individuals involved - harmonic (e.g. protocooperation ants and sucking insects) or when at least one is harmed - disharmonious (e.g. predation or competition) (Leite et al. 2012). It is evaluated the ecological indices (abundance, diversity, and species richness) and interactions between the groups of arthropods on P. regnellii leaf surface, during 24 months, in a degraded area.

The work was carried out in a degraded area of the “Instituto de Ciências Agrárias da Universidade Federal de Minas Gerais (ICA/UFMG)” in the municipality of Montes Claros, Minas Gerais state, Brazil (latitude 16º 51' 38" S, longitude 44º 55' 00" W, altitude 943 m) for 24 months (April 2015 to March 2017). The climate of this area, according to the Köppen climate classification, is tropical dry, with annual precipitation between 1000 and 1300 mm, dry winter and average annual temperature ≥ 18 ºC. The soil is Neosol Litolic with an Alic horizon (Silva et al. 2020).

The P. regnellii seedlings were planted in hole (40 x 40 x 40 cm) when they were 30 cm high, with a 2-meter spacing between them. The soil was corrected with dolomitic limestone, increasing base saturation to 50 %, natural phosphate, gypsum, FTE (Fritted Trace Elements), potassium chloride and micronutrients equivalent to the need determined in the soil analysis. A total of 20 L of dehydrated sewage sludge was placed in each hole (single dose) and the biochemical characteristics of this fertilizer have been reported (Silva et al. 2020). In March 2014, P. regnellii seedlings were prepared in a nursery in plastic bags (16 x 24 cm) with reactive natural phosphate mixed with the substrate at a dosage of 160 g, which were then planted in the final location in September of the same year. The seedlings were irrigated twice a week until the beginning of the rainy season (October). The design was completely randomized with 48 replications (plants), with the adaxial and abaxial leaf faces as the treatments.

Arthropods were counted on the leaf faces (adaxial and abaxial) between 7:00 and 11:00 a.m. on vertical axis (apical, middle and basal parts) and horizontal axis (north, south, east and west) of the canopy, totaling 12 leaves/plant/evaluation, in the 48 P. regnellii plants, six months of age, for 24 months. The insects captured were stored in flasks with 70 % alcohol, separated into morphospecies and sent for identification.

Data was reduced by calculating averages per replication (plant). The ecological indices (abundance, diversity and species richness) were calculated per species identified in the treatments (adaxial and abaxial faces) using the BioDiversity Professional software, Version 2 (Krebs 1998). Abundance and species richness are the total number of individuals and species, respectively, in a sampling unit. Diversity was calculated using the Hill’ formula (1^st order): N1= exp (H’), where H’ is the Shannon-Weaver diversity index, calculating the diversity with the actual species number.

Data for abundance, diversity and species richness of arthropod groups (e.g. phytophagous) were subjected to a non-parametric statistical hypothesis, the Wilcoxon signed rank test (P<0.05), using the System for Analysis Statistics and Genetics (SAEG) statistical program, version 9.1 (SAEG 2007) (Supplier: “Universidade Federal de Viçosa”). The interactions between the arthropod groups were assessed by Spearman correlations (P<0.05) using this program.

The highest numbers of phytophagous insects Orthoptera Tettigoniidae and Tropidacris collaris (Romaleidae), and Hemiptera Pentatomidae; that of natural enemies Hymenoptera Camponotus sp. and Pseudomyrmex termitarius (Formicidae), and Diptera dolichopodidae; and abundance and species richness of chewing insects and protocooperanting ants were observed in the P. regnellii adaxial leaf face. The sucking insect Phenacoccus sp. (Hemiptera: Pseudococcidae) (≈0.37), chewing insect T. collaris (≈0.16) and the natural enemy Araneidae (≈0.52) were the arthropods with highest numbers of on P. regnellii leaves (table 1). The abundance of spiders correlated, positively, with that of chewing insects (r = 0.18, P = 0.04, n = 96), and the number of spiders with that of T. collaris (r = 0.23, P = 0.01, n = 96) on P. regnellii plants.

Table 1
Number of individuals (average ± SE) per specie, abundance, diversity, and species richness of phytophagous and pollinator insects and natural enemies in the adaxial and abaxial leaf faces on Platycyamus regnellii (Fabaceae)/plant

^*TW= Test of Wilcoxon. ^§VT= value of test. n= 48 per treatment. --- = not generated.

Phytophagous (Class Insecta)	Leaf face		TW*
	Abaxial	Adaxial	VT§	P
Coleoptera (Chrysomelidae): Alagoasa sp.	0.00 ± 0.00	0.04 ± 0.04	1.00	0.15
Eumolpus sp.	0.04 ± 0.02	0.02 ± 0.02	0.58	0.27
Walterianela sp.	0.02 ± 0.02	0.08 ± 0.04	1.37	0.08
Wanderbiltiana sp	0.06 ± 0.03	0.04 ± 0.04	0.98	0.16
Curculionidae: Lordops sp.	0.04 ± 0.02	0.02 ± 0.02	0.59	0.27
Lepidoptera	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Orthoptera (Tettigoniidae)	0.00 ± 0.00	0.27 ± 0.08	3.50	0.00
Romaleidae: Tropidacris collaris	0.04 ± 0.02	0.27 ± 0.08	2.47	0.01
Abundance of chewing insects	0.77 ± 0.14	0.21 ± 0.06	3.26	0.00
Diversity of chewing insects	0.25 ± 0.12	0.20 ± 0.09	0.04	0.49
Species richness of chewing insects	0.63 ± 0.10	0.21 ± 0.06	3.15	0.00
Sucking insects
Hemiptera (Aleyrodidae)	0.46 ± 0.26	0.04 ± 0.02	0.91	0.18
Cicadellidae: Balclutha hebe	0.00 ± 0.00	0.04 ± 0.02	1.42	0.07
Erythrogonia sexguttata	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Nogodinidae: Bladina sp.	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Pentatomidae	0.00 ± 0.00	0.21 ± 0.06	3.13	0.00
Pseudococcidae: Phenacoccus sp.	0.73 ± 0.51	0.00 ± 0.00	1.42	0.07
Abundance of sucking insects	0.33 ± 0.09	1.19 ± 0.56	1.01	0.16
Diversity of sucking insects	---	---	---	---
Species richness of sucking insects	0.31 ± 0.09	0.13 ± 0.04	1.46	0.07
Pollinator (Class Insecta)
Hymenoptera (Apidae): Apis mellifera	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Natural enemies (Classes Arachnida and Insecta)
Araneidae	0.02 ± 0.02	1.02 ± 0.93	1.39	0.08
Oxyopidae	0.00 ± 0.00	0.04 ± 0.02	1.42	0.07
Oxyopes saliticus	0.08 ± 0.04	0.04 ± 0.02	0.83	0.20
Salticidae	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Aphirape uncifera	0.08 ± 0.04	0.02 ± 0.02	1.37	0.08
Uspachus sp.	0.02 ± 0.02	0.02 ± 0.02	0.00	0.50
Sparassidae: Quemedice sp.	0.02 ± 0.02	0.08 ± 0.05	1.03	0.15
Tetragnathidae: Leucauge sp.	0.02 ± 0.02	0.06 ± 0.04	0.59	0.27
Thomisidae: Tmarus sp.	0.04 ± 0.02	0.00 ± 0.00	1.42	0.07
Aphantochilus rogersi	0.04 ± 0.02	0.00 ± 0.00	1.42	0.07
Abundance of spiders	1.31 ± 0.93	0.33 ± 0.09	0.35	0.37
Diversity of spiders	0.17 ± 0.06	0.23 ± 0.10	0.07	0.47
Species richness of spiders	0.33 ± 0.08	0.45 ± 0.15	0.09	0.47
Diptera (Dolichopodidae)	0.00 ± 0.00	0.17 ± 0.07	2.52	0.01
Hymenoptera (Braconidae)	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Vespidae: Polybia sp.	0.00 ± 0.00	0.02 ± 0.02	1.0	0.15
Formicidae: Brachymyrmex sp.	0.02 ± 0.02	0.04 ± 0.02	0.58	0.27
Camponotus sp.	0.00 ± 0.00	0.15 ± 0.05	2.73	0.00
Cephalotes sp.	0.00 ± 0.00	0.04 ± 0.04	1.00	0.15
Ectatoma sp.	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Pheidole sp.	0.00 ± 0.00	0.02 ± 0.02	1.00	0.15
Pseudomyrmex termitarius	0.00 ± 0.00	0.10 ± 0.04	2.29	0.01
Abundance of protocooperanting ants	0.38 ± 0.10	0.02 ± 0.02	3.64	0.00
Diversity of protocooperanting ants	0.03 ± 0.03	0.03 ± 0.03	0.00	0.50
Species richness of protocooperanting ants	0.35 ± 0.09	0.02 ± 0.02	3.64	0.00

Recently, research in Brazil reported the sucking insect Phenacoccus sp. (Hemiptera: Pseudococcidae) as the most abundant phytophagous on P. regnellii plants (Souza et al. 2021) and with the highest porcentage Importance Index-Production Unknow on leaves of P. regnellii (Leite 2022).

The greatest numbers of the phytophagous insects Pentatomidae, Tettigoniidae, and T. collaris, and of the natural enemies Camponotus sp., Dolichopodidae, and P. termitarius, and the abundance and species richness of chewing insects and protocooperanting ants, were noted in the adaxial leaf face on P. regnellii plants is, probably, due to the lowest force applied by these arthropods to remain on this face and the absence of trichomes on them. The choice of the adaxial leaf face, perhaps, is due to the leaf characteristics of the P. regnellii plants, which are tri-foliate pinnate (in the form of a feather) with elliptical lateral leaflets (9-15 cm long and 6.5-10 cm wide) and the central is largely elliptical (14-25 in length and 10-19 cm in width) and, mainly, with dense hair in the abaxial (Moura et al. 2016), maybe as a source of resistance to most arthropods in this last leaf surface. Host plant leaf characteristics such as hairiness, regular shape or not, roughness, wax content, and type and number of veins can affect the insect, choosing the leaf face (adaxial or abaxial) that requires less force applied to walking (Salerno et al. 2018).

The largest numbers Phenacoccus sp. on P. regnellii plants can be a problem due to this sucking insect is related as pest of Abelmoschus esculentus (Malvaceae), Amaranthus flavus (Amaranthaceae), Bidens pilosa (Asteraceae), Carica papaya (Caricaceae), Gossypium hirsutum (Malvaceae), Manihot esculenta (Euphorbiaceae), Solanum lycopersicum (Solanaceae), and Vitis vinifera (Vitaceae). This insect causes necrosis in the apical tissues, reduces the photosynthetic rate, leaf growth (with yellowing and fall of these), negatively affecting the plant production (e.g. M. esculenta) (Schulthess 1991, Culik et al. 2007 and Santos and Peronti 2017). The biggest numbers of the chewing insect T. collaris on P. regnellii plants confirms its polyphagy, which has been reported to damage plants of Acacia mangium (Fabaceae), Casuarina glauca (Casuarinaceae), and Leucaena leucocephala (Fabaceae) (Poderoso et al. 2013, Damascena et al. 2017 and Silva et al. 2020). The highlight of spiders, Araneidae family, on P. regnellii plants, is due to their generalist predatory habit, reducing damage by insects, mainly defoliators, in USA agroecosystems (Landis et al. 2000), in Caryocar brasiliense (Caryocaraceae) trees, in cerrado and pasture areas, in Brazil (Leite et al. 2012), in silvopastoral systems L. leucocephala - Megathyrsus maximus (Poaceae) in Cuba (Valenciaga et al. 2020), and those of Lycosidae and Linyphiidae in Hordeum vulgare (Poaceae) fields in different landscapes in Uppsala, Switzerland (Öberg et al. 2008), Ctenidae in Italy (Venturino et al. 2008) and Oxyopidae on A. mangium trees (Silva et al. 2020).

The positive correlation between the abundance of spiders and that of chewing insects and the number of spiders with that of T. collaris on P. regnellii plants is, probably, due to predators following their prey, as observed on C. brasiliense, L. leucocephala, and Pistacia lentiscus (Anacardiaceae) trees (Damascena et al. 2017). Spiders prey on insects in natural and agricultural systems (Venturino et al. 2008), often reducing defoliation and mines in plants, as related in C. brasiliense trees (Leite et al. 2012).

It is concluded that the greatest species richness and numbers of chewing insects (e.g. T. collaris) and protocooperanting ants (e.g. P. termitarius) on the adaxial leaf face on P. regnellii plants are, probably, due to the lowest force required for walking and absence of trichomes (e.g. resistance factor). The largest numbers of Phenacoccus sp. and T. collaris in P. regnellii plants is a cause for concern, as these insects are pests in several cultures. Spiders (e.g. Araneidae), natural enemies, showed greatest numbers of individuals in leaves on P. regnellii plants and followed their prey, being important in biological control.

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Author notes

*Email: nvalenciaga1966@gmail.com

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