Amblyomma mixtum free-living stages: Summer and winter use, preference, and niche width in an agroecosystem (Yopal, Casanare, Colombia)

Studying a species’ tolerance to an ecosystem’s environmental conditions and its selection of available resources is relevant in ecological and evolutionary terms. Moreover, formulation of effective control strategies implicitly includes the study of habitat use and preference and niche width in anthropogenically transformed natural landscapes. Here, we evaluated whether the use, habitat preference, and niche range of the Amblyomma mixtum tick changed between stages, habitats, and seasons (summer-winter 2019) on a farm in Yopal (Casanare, Colombia). To this end, the presence and relative abundance of larvae, nymphs, and free-living adults was quantified in four different habitats according to the type of vegetation cover (Riparian Forest, Cocoa Crop, King Grass Crop, and Star Grass Paddock). Habitat availability was calculated, environmental variables were analyzed, and various indices of habitat use and preference and niche width were calculated. A. mixtum’s habitat use and preference and niche width changed between stages, habitat types, and time of the year. The total abundance of A. mixtum was an order of magnitude greater in summer than winter. Nymphs and larvae dominated it in the summer and adults in the winter. In summer, all the stages used the four habitats. In winter, the larvae did not use two habitats (Riparian Forest and Cocoa Crop); nymphs did not use the cocoa crop. A. mixtum adults used all the habitats in both seasons. In summer, the nymphs and larvae preferred three of the four habitats (King Grass Crop, Star Grass Paddock, and Cocoa Crops), while adults preferred the King Grass Crop. In winter, the nymphs and larvae preferred the King Grass Crop and Star Grass Paddock, while the adults preferred the King Grass Crop. The value of the niche width index was high for larvae, nymphs, and adults in summer, while it was high only for adults in winter. A. mixtum is exposed to significant daily, seasonal, and multiannual variations in relative humidity (minimum 30%), ambient temperature (minimum 18°C), solar radiation (maximum 800 W/m2), and precipitation (maximum 481 mm/month). Thus, the local A. mixtum population could rapidly acclimatize to changing habitats (unstable or temporary) under fluctuating environmental conditions (e.g., King Grass Crop). However, the winter flood season in Yopal could exceed A. mixtum’s adaptive capacity during its most vulnerable stages. Mathematically, a low number of female A. mixtum, surviving the most demanding environmental conditions, could sufficiently ensure the population’s persistence, which, coupled with the vast host range, could facilitate the ticks stages’ dispersal among habitats to complete their life cycle. A. mixtum’s population control should be carried out during its season of greater vulnerability (winter), when the population is low, particularly the females.


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223 Within each habitat category, the CO 2 trap and white flannel dragging transect sampling units 224 (grouping all the individuals captured by trap or transect) were located at convenience, following 225 biological criteria (biology and pattern of tick activity and the probability of being a human vector), 226 with replicates for each habitat (where abundance and presence-use response variables were 227 measured). The habitat fragments, patches, and paddocks, chosen and sampled from the 228 photomosaic, favored those within a radius of approximately 500 m from the buildings of the 229 Matepantano farm, including the places frequently used for work and agropastoral practices (Figs 1 230 and 2). The number of traps and transects were fairly similar between habitats to facilitate comparison 231 of relative abundances. Random sampling was not used for the location of the sampling units (trap 232 or transect) in the vegetation types because, as indicated by other authors [3], this usually results in 233 few or no observations of habitat use.

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235 Generalities of the compared habitats 236 Riparian Forest (5.32224º N and 72.28696º W). This habitat was a gallery forest bordered 237 by a permanent creek and dominated by adults and juveniles of the Attalea butyracea (Arecaceae) 238 palm, a closed canopy, and an open understory (Table 1). There was no apparent change in 239 vegetation structure between summer and winter (stable structure), with saturated soil in winter and 240 litter in both seasons. Tick abundance sampling was conducted between 2 and 8 m into the forest, 241 outside the edge zone. Soil dominant fraction Clay soil with some sand.
The soil has acidic pH.
Clay soil with few silt and fine sand soils.
Clay soil.

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Cocoa Crop (5.32312º N and 72.28691º W). This habitat was a cacao crop (Theobroma 246 cacao). The farm used the tresbolillo technique to plant the cocoa. This technique entails locating the 247 plants in a triangular shape with a distance of 3.5 x 3.5 m between them. The crop was mixed with 248 Acacia trees to provide shade (Table 1), in addition to some banana plants. In summer, the crop soil 249 was dry (cracked), with leaf litter and dehydrated plants caused by a couple of months of drought 250 (december-january). In winter, the soil was saturated, and the vegetation was green. Leaf litter was 251 observed in both summer and winter.

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King Grass Crop (5.32482º N and 72.28704º W). This habitat was a King Grass plantation 253 (Pennisetum hybridum). In summer, the grass was dry (yellow) and uncontrolled, sometimes broken, 254 but dense, with a height of between 1 and 2 m and interspersed with thorny shrubs and very few 255 scattered trees (Table 1). In winter, the same pasture was green (1.8 m high), and the soil was wet 256 from rainfall. The search for ticks was conditioned by accessibility and the possibility of placing the 257 bases of the CO 2 traps among the dense grassland. However, the collection points were distributed 258 broadly over the habitat patches.

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The niche width indices were applied to infer whether the habitat resources were used or 339 exploited uniformly (or asymmetrically) by the observed species and the conditions that allow its 340 survival there. In this study, we measured how much wider the spectrum of resources used was in 341 the habitat and how a species could potentially live in a broad range of conditions; this was indicated 342 by its relative abundance (proxy), and the number of habitats inhabited [14]. Regarding the latter, 14 343 resources and conditions should be considered as a whole, without specific differentiation, which is 344 impossible.

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There is not enough published information about A. mixtum regarding its life history and 346 autoecology (species-resources-condition-habitat relationships) in the current literature. The Havistat 347 program has been successfully employed in other biological research [8,[76][77][78][79]. By reaching a 348 consensus among the indices, it is possible to differentiate whether a species uses one habitat or 349 several, and, therefore, its resources), if it prefers that habitat (or others) or strongly selects or avoids 350 one or more particular habitats. According to [62], resources are "avoided" in a habitat when resource 351 use (relative abundance) is disproportionately less than expected, based on the availability of that 480 winter compared to the remnant stages (Table 2). Up to 17 times more nymphs and 25 times more 481 adults were collected using the CO 2 traps than in the transects in summer. Similarly, six times more 482 nymphs and 20 times more adults were captured in winter using CO 2 traps than flannel dragging. In 483 all habitats, CO 2 traps were more effective in collecting ticks in summer; in winter, they were effective 484 in 75% of the habitats. The transects only outperformed the traps in capturing ticks in the Star Grass 485 paddock habitat in winter (

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A. mixtum uses, but does not prefer, the Riparian Forest habitat. This result was consistent 497 for nymphs, larvae, and adults, which was corroborated by the interpretation of II index that indicated 498 a strong avoidance of this habitat (Table 5). Although adults also preferred the King Grass plantation 499 habitat in both seasons, according to all selected indices, in summer, they used, but did not prefer 500 the cocoa plantation and Star Grass Paddock, according to four of the five indices (Table 4). In winter, 501 the concordance of non-preference of adults decreases between indices with respect to the habitat 502 'Cocoa Crop' but remains with respect to 'Star Grass Paddock'. The interpretation index of II shows 503 a strong avoidance of the habitat 'Riparian Forest ' by the adults (Table 4). In the case of larvae and 504 nymphs in summer the concordance of preference between indices is not complete either. Larvae 505 and nymphs prefer three of the four habitats according to three of the five selected indices. In winter 506 the five indices coincided in indicating preference of the immature stages for the habitats 'Star Grass 507 Paddock' and ' King Grass Crop' (Table 4).

509 Niche width 510
In summer, the niche amplitude was maximum for the larvae in four of the five indices, as the 511 value of Ivlev's electivity index was the lowest. In general, the rates of niche width obtained in this 512 part of the year are considered high for all free-living stages of A. mixtum, as well as the population 513 as a whole, since the values obtained tend towards the maximum amplitude (Table 5) [65,72,73,75].

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514 Interestingly, during the winter season, the five selected indices coincided in a maximum niche 515 amplitude for the adult stage (Table 5), which also coincides with similar abundance data for adults 516 in the two sampled seasons (Table 2). That is, in summer and winter the survival rate of adults was 517 similar and could indicate that adults are present at different times throughout the year. In contrast, 518 the population of larvae and nymphs almost succumbed in winter, reducing their numbers by one 519 order of magnitude when compared to their collection in summer and disappearing from the 'Cocoa 520 Plantation' habitat. The larvae were also not found in the 'Riparian Forest' habitat ( Figure 3 and Table   521 2).

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Remarkably, the larvae in winter obtained the lowest niche amplitude in all the selected 523 indices (   (Table 6) and an absolute range of 26ºC at the 535 local weather station located in the 'Cocoa Plantation' habitat ( Table 7). The temperature variation in 536 summer at the Matepantano farm is wider (from 18ºC to 37ºC) when compared to the winter season 537 (minimum of 19ºC and maximum of 33.6ºC). Total precipitation in winter (August) was one order of 538 magnitude higher than in summer (Table 7). The average relative humidity varied by 20% between 539 February and August, both in the regional (61 and 81%) and local (68 and 88%) climate seasons, 540 reaching minimum values of 30% in the summer season (Tables 6 and 7).

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The relative humidity varied by 40% from the first part of the morning until midday, but in the 583 afternoon, it increased by almost 10% from 30%. Thus, the relative humidity can vary up to 50% in a 584 single day in the habitat of 'Cocoa Crop' (Figure 5). This one-day variation was half of the variation 585 recorded in seven years for temperature and 75% of the variation recorded multiyearly for humidity 586 (Table 7). Ticks in this environment should survive extremely low humidity conditions of up to 30% 587 when there is more solar radiation. The relative humidity decreased as the temperature increased.
588 Higher values of relative humidity, early in the morning, coincided with observations of increased tick 589 activity and abundance in the dry ice traps at the time of capture.

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Variations were between 1.100 and 300 W/m 2 , which means a difference of 800 W/m 2 , 593 decreasing towards the sunset. On the other hand, the temperature remained high on average at 594 35ºC, decreasing little in the afternoon hours. Therefore, the range of variation was lower (5ºC) in the 595 afternoon than that observed in the morning for the habitat 'Cocoa Crop' at the same time ( Figure 5).

596
The relative humidity in 'Star Grass Paddock' was low in summer, 34% on average and at least 32%, 597 but equally the variation between extreme values was low, only 6% ( Figure 5).

600
In this habitat, solar irradiation was very low (one order of magnitude lower), with an average 601 of 36 W/m 2 and a variation between extreme values of 180 W/m 2 ( Figure 5). This low penetration of 602 sunlight, due to the high coverage of the canopy, maintained a relatively constant temperature with 603 an average of 31ºC, varying only 2ºC. Unfortunately, due to damage to the humidity sensor, the 604 respective values were not recorded that day.