Table 4 Summary of interpretation of adaptation strategies given shape, soil, and body size
Taxa | Soil type occupied | Digging strategy used | Evolutionary comments |
|---|---|---|---|
T (T.) mazama | Soft sandy soil - low clay, bulk density, and linear extensibility; high sand make this relatively easy to dig in | Ancestral claw-digging | Likely illustrates the primitive ancestral condition except in lateral humeral shape. |
T (T.) monticola | Soft sandy soil - lowest clay, bulk density, and linear extensibility; highest sand in the genus | Ancestral claw-digging | Arguably the easiest soil in the region, likely preserves the primitive ancestral condition for the genus. |
T (T.) talpoides fisherii | Friable clay soil - medium clay but high sand and low bulk density suggests it is not very compacted | Derived tooth-digging despite body size | While still appears to tooth-dig, like sister subspecies below, may be shifting back towards claw-digging in sandier soils |
T (T.) talpoides quadratus | Hard clayey soil - high clay and very low sand, low bulk density suggests it is not very compacted | Derived tooth-digging despite body size | A combination of allometric and non-allometric cranial rearrangement appears to produce derived tooth-digging shape |
T. (M.) b. canus (Townsendii clade) | Heavy sandy soil - low clay and high sand suggests the latter drives high bulk density | Claw digging despite body size | Intermediate soil appears to have selected for more for claw-digging adaptations |
T. (M.) townsendii | Heavy sandy soil - more clay than sister species above but still high sand | Tooth-digging via size-increase alone | In contrast to sister species above, intermediate soil appears to have selected more for tooth-digging adaptations |
T. (M.) bottae laticeps | Friable clay soil - medium clay but high sand and low bulk density make it easier to manipulate | Claw-digging despite body size | Diverging from the rest of its clade, intermediate soil appears to have selected for claw-digging adaptations |
T. (M.) bottae navus | Friable clay soil - medium clay and medium bulk density but high sand make it easier to manipulate | Derived tooth-digging | In contrast to sister subspecies above, intermediate soil appears to have selected for tooth-digging adaptations |
T. (M.) bottae leucodon | High clay soil - highest clay and linear extensibility with low sand and low bulk density | Derived tooth-digging | Arguably the hardest soils in the region appear to have selected for both tooth- and claw-digging adaptations |
T. (M.) bottae saxatilis | High clay soil - medium clay and linear extensibility with low sand and high bulk density | Derived tooth-digging | In slight contrast to sister subspecies, hard soils appear to have selected for a slightly more procumbent tooth-digging shape & less emphasis on claw-digging |