1 1 Supplementary materials 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 2 33 Table S1 34 Description of the Collembola response traits considered in our study. All morphological traits were measured on specimens (when required, 35 mouthpart structure was confirmed using existing literature). Sexual reproduction (life-history trait) was determined at population level and 36 confirmed using existing literature. Aggregated traits (microhabitat preference and dispersal ability) were determined based on associations of 37 various morphological traits. Hypotheses for each trait are based on the references cited below †. 38 Attribute(s) (code) Trait Definition / Measurement Supposed function(s) [data type] Morphological traits Body length Distance between anterior part of head and Larger species live more on the soil surface, are more Measured value (BL ) end of abdomen (no furcula and antennae) xerophilic and have a higher food resource use [continuous – mm] Relative leg Ratio of the third leg length to the body Relatively longer legs are overall present in surface- length ( RLL ) length dwelling species and permit a faster dispersal Measured value Body shape ratio Ratio of the body length to the largest body Species with a higher ratio can migrate deeper in the soil [continuous - proportion] (BSR ) width (soil-dwelling species have a more slender body shape) Relative furcula Surface-dwelling species have overall a relatively longer Measured value Ratio of the furcula length to the body length length ( RFL ) furcula permitting them to jump further to escape predators [continuous - proportion] Relative antennae Ratio of the antennae length to the head Measured value length ( RAL ) length [continuous - proportion] Bothriotricha Modified setae (trichobothria) present on the Absence (0) / Presence (1) Relatively longer antennae, presence of bothriotricha and a abdomen [binary] (BOP ) higher number of ocelli provide a better detection of the physicochemical conditions on the soil surface (e.g., air 0+0 ocelli (0) movement, chemical compounds, microclimate, light). 1+1 or 2+2 ocelli (1) Ocelli number 3+3 or 4+4 ocelli (2) Number of ocelli per eye Relatively longer antennae and 8 ocelli permit also faster (ON ) dispersal. The PAO fulfils the above sensorial functions in 5+5 or 6+6 ocelli (3) species living deeper in the soil 7+7 or 8+8 ocelli (4) [ordinal] Post-antennal Sensory organ present between eye and Absence (0) / Presence (1) organ ( PAO ) antennae [binary] Body A higher pigmentation and the presence of scales provide Unpigmented (0) Pigments present into the cuticle with / better protection against UV-light and dry conditions, body Coloured, no pattern (0.5) pigmentation without the presence of a clear pattern temperature control, camouflage as well as escape from Coloured with pattern (1) level ( BPL ) predators (scales can be lost when caught by a predator) [ordinal] 3 Scales Notably for surface-dwelling species Absence (0) / Presence (1) Modified setae present on any body part (SP ) [binary] Morphology of the mandible and maxilla: Related to the main food resources available: Mouthpart - Reduced: no mandibular molar plates reduced mouthparts are more associated with necrophagy Reduced (0) - Normal: molar plates present, maxilla with (scavengers) and carnivory (e.g ., nematodes), while Normal (0.5) structure tridentate capitulum and six ciliate lamellae normal mouthparts are more associated with microbivory Strong (1) (MPS ) - Strong: molar plates present, maxilla head (fungal hyphae and bacteria) and strong mouthparts with [ordinal] with enlarged lamellae having strong fringes micro-detritivory (litter colonized by microflora) Life-history trait Parthenogenesis is favoured in species living in more Sexual Determined by the percentage of male and stable conditions such as in deeper soil (euedaphic Parthenogenesis (0) / reproduction female individuals in populations (sex ratio). species), while the survival in more unstable conditions Sexual reproduction (1) Parthenogenetic reproduction (thelytoky) was strategy such as at the soil surface (surface-dwelling species) is [binary] assumed when only females were found (SRS ) favoured by sexual reproduction Aggregated traits* - Euedaphic species (body length < community median body length, ocelli number < 1, PAO Functional roles of species related to their vertical position Euedaphic (EU) Microhabitat present and no pigmentation present) (stratification): Hemiedaphic (HEMI) preference - Hemiedaphic species (intermediate modalities) soil-dwelling species (euedaphic) Epedaphic (EPI) - Epedaphic species (body length > community litter-dwelling species (hemiedaphic) (MH ) [categorical] median body length, ocelli number > 1, no PAO surface-dwelling species (epedaphic) and pigmentation present) Dispersal - High dispersal ability (relative antennae and leg lengths > community median relative Low (0) / High (1) ability Morphological capacity of species to disperse antennae and leg lengths and ocelli number = 8) [categorical] (DA ) - Low dispersal ability (other cases) 39 † BL (Makkonen et al. , 2011; Huebner et al. , 2012; Lindo et al. , 2012; Malmström, 2012; Farská et al. , 2014a,b; Salmon et al. , 2014; Santorufo et al. , 2014; 40 Widenfalk et al. , 2016) - RLL (Ponge et al. , 2006; Salmon et al. , 2014) - BSR (Salmon et al. , 2014) - RFL (Vanderwalle et al. , 2010; Makkonen et al. , 2011; 41 Huebner et al. , 2012; Martins da Silva et al. , 2012; Farská et al. , 2014a,b; Salmon et al. , 2014; Santorufo et al. , 2014) - SP (Vanderwalle et al. , 2010; Makkonen 42 et al. , 2011; Huebner et al. , 2012; Martins da Silva et al. , 2012; Salmon et al. , 2014) - RAL (Ponge et al. , 2006; Vanderwalle et al. , 2010; Makkonen et al. , 2011; 43 Huebner et al. , 2012; Martins da Silva et al. , 2012; Salmon et al. , 2014; Widenfalk et al. , 2016) - BOP (Vanderwalle et al. , 2010; Salmon et al. , 2014) - ON 44 (Ponge et al. , 2006; Vanderwalle et al. , 2010; Makkonen et al. , 2011; Huebner et al. , 2012; Martins da Silva et al. , 2012; Salmon et al. , 2014) - PAO (Huebner et 45 al. , 2012; Salmon et al. , 2014) - BPL (Vanderwalle et al. , 2010; Makkonen et al. , 2011; Huebner et al. , 2012; Martins da Silva et al. , 2012; Salmon et al. , 2014; 46 Santorufo et al. , 2014) - MPS (Fjellberg, 1998, 2007; Santorufo et al. , 2014; Malcicka et al. , 2017) - SRS (Lindberg and Bengtsson, 2005, 2006; Chahartaghi et 47 al. , 2009; Hågvar, 2010; Huebner et al. , 2012; Malmström, 2012; Lindo et al. , 2012; Farská et al. , 2013, 2014a,b; Salmon et al. , 2014; Santorufo et al. , 2014) - 4 48 MH (Lindberg and Bengtsson, 2005, 2006; Hågvar, 2010; Vanderwalle et al. , 2010; Bokhorst et al. , 2012, 2014; Malmström, 2012; Martins da Silva et al. , 2012; 49 Farská et al. , 2013, 2014a,b; Widenfalk et al. , 2016) - DA (Ojala and Huhta, 2001; Ponge et al. , 2006; Malmström, 2012) 50 * Microhabitat preference was assessed using body length, ocelli number, pigmentation level and presence of a post-antennal organ (Vanderwalle et al. , 2010; 51 Martins da Silva et al. , 2012; Widenfalk et al. , 2016). Dispersal ability was inferred using the relative lengths of antennae and legs and the number of ocelli: 52 species with longer antennae and legs plus 8 ocelli (complete visual apparatus) should generally disperse faster (Ponge et al ., 2006). The furcula length was not 53 considered here because this appendage is not directly involved in dispersal ability (Bauer and Christian, 1987). 5 54 Table S2 55 Description of the Oribatida response traits considered in our study. All morphological traits were measured on specimens (when required, 56 mouthpart structure was confirmed using existing literature). Sexual reproduction (life-history trait) was determined at population level and 57 confirmed using existing literature. Aggregated traits (microhabitat preference and dispersal ability) were determined based on associations of 58 various morphological traits. Hypotheses for each trait are based on the references cited below †. 59 Attribute(s) (code) Trait Definition / Measurement Supposed function(s) [data type] Morphological traits Body Distance between the anterior part of the Larger species live more on the soil surface, are more Measured value length ( BL ) rostrum to the end of the notogaster xerophilic and have a higher food resource use [continuous - mm] Species with a higher ratio can migrate deeper in the Body shape Ratio of the body length to the largest width Measured value soil (soil-dwelling species have a more slender body of the notogaster [continuous - mm] ratio ( BSR ) shape) Ratio of the claw length (median claw Relative claw Measured value considered if 3 claws present) of the first Three short claws permit easier and possibly faster [continuous - mm] length ( RCL ) pair of legs to the body length displacement in more complex and unstable conditions 1 claw (1) such as at the soil surface while one long claw is more Claws number 2 claws (2) Number of claws of the first pair of legs associated with stable conditions of deeper soil (CN ) 3 claws (3) [ordinal) Relative Used to detect soil physical conditions (e.g., air Ratio of the sensillus length to the body Measured value sensillus movement), the sensillus is generally shorter in length [continuous - proportion] length ( RSL ) surface-dwelling species Presence of extension of the cuticle on the The presence of pteromorphae provides a better water Pteromorphae Absence (0) / Presence (1) anterior part of the notogaster (humeral