Within-population beta diversity
In general, nMDS based on Bray-Curtis and Euclidean distances revealed
similar clustering patterns. The nMDS plots including pre- and
post-disturbance data reflected a strong clustering by time (Figure 4A,
B, E, F). However, when corrected for the temporal effect, there were
also clear effects of temperature (Figure 4C, G) and range (Figure 4D,
H). These observations were also supported by the mGLM fitted on
post-disturbance time points. Community composition differed with time,
between temperatures, between ranges (p = 0.002), and also the
interaction between temperature and range was significant (p = 0.012,
Table S2c).
Beta diversity within-populations (based on Bray-Curtis and Euclidean
distances) increased from field to the climate room
(pBray-Curtis = 0.024,
pEuclidean = 0.004) but did not differ between
ranges (p ≥ 0.525) and declined sharply following the disturbance
treatment (p < 0.001, Figure 3K, P). After the disturbance,
within-population beta diversity varied with time (p < 0.001)
and followed an increasing trend (Figure 3L, M, Q, R) that was best
fitted with a polynomial function (Table S3). Distances did not vary
significantly between ranges (p ≥ 0.137). The main effect of temperature
was highly significant for both distance measures, with substantially
higher within-population beta diversity at 22 °C, compared to 15 °C (p
< 0.001, Figure 3N, S). In addition, significant p-values were
found for the interactions between range and time(pBray-Curtis = 0.015,
pEuclidean < 0.001), temperature and
time (p < 0.001), and range and temperature (p ≤
0.001). Post-hoc comparisons indicated that the significant interaction
between range and temperature was explained by higher beta diversity at
22 °C in native populations compared to non-natives
°C(pBray-Curtis = 0.004,
pEuclidean < 0.001), whereas natives
and non-natives did not differ in terms of within-population beta
diversity at 15 °C (Figure 3O, T, see Table S2d for all statistical
output).