| 1. |
- Outomuro, David, et al.
(författare)
-
A potential pitfall in studies of biological shape : Does size matter?
- 2017
-
Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 86:6, s. 1447-1457
-
Forskningsöversikt (refereegranskat)abstract
- 1. The number of published studies using geometric morphometrics (GM) for analysing biological shape has increased steadily since the beginning of the 1990s, covering multiple research areas such as ecology, evolution, development, taxonomy and palaeontology. Unfortunately, we have observed that many published studies using GM do not evaluate the potential allometric effects of size on shape, which normally require consideration or assessment. This might lead to misinterpretations and flawed conclusions in certain cases, especially when size effects explain a large part of the shape variation. 2. We assessed, for the first time and in a systematic manner, how often published studies that have applied GM consider the potential effects of allometry on shape. 3. We reviewed the 300 most recent published papers that used GM for studying biological shape. We also estimated how much of the shape variation was explained by allometric effects in the reviewed papers. 4. More than one-third (38%) of the reviewed studies did not consider the allometric component of shape variation. In studies where the allometric component was taken into account, it was significant in 88% of the cases, explaining up to 87.3% of total shape variation. We believe that one reason that may cause the observed results is a misunderstanding of the process that superimposes landmark configurations, i.e. the Generalized Procrustes Analysis, which removes isometric effects of size on shape, but not allometric effects. 5. Allometry can be a crucial component of shape variation. We urge authors to address, and report, size effects in studies of biological shape. However, we do not propose to always remove size effects, but rather to evaluate the research question with and without the allometric component of shape variation. This approach can certainly provide a thorough understanding of how much size contributes to the observed shaped variation.
|
|
| 2. |
- Sniegula, Szymon, et al.
(författare)
-
Seasonal time constraints reduce genetic variation in life-history traits along a latitudinal gradient
- 2016
-
Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 85:1, s. 187-198
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Time constraints cause strong selection on life-history traits, because populations need to complete their life cycles within a shorter time. We therefore expect lower genetic variation in these traits in high-than in low-latitude populations, since the former are more time-constrained. 2. The aim was to estimate life-history traits and their genetic variation in an obligately univoltine damselfly along a latitudinal gradient of 2730 km. 3. Populations were grown in the laboratory at temperatures and photoperiods simulating those at their place of origin. In a complementary experiment, individuals from the same families were grown in constant temperature and photoperiod that mimicked average conditions across the latitude. 4. Development time and size was faster and smaller, respectively, and growth rate was higher at northern latitudes. Additive genetic variance was very low for life-history traits, and estimates for egg development time and larval growth rate showed significant decreases towards northern latitudes. The expression of genetic effects in life-history traits differed considerably when individuals were grown in constant rather than simulated and naturally variable conditions. 5. Our results support strong selection by time constraints. They also highlight the importance of growing organisms in their native environment for correct estimates of genetic variance at their place of origin. Our results also suggest that the evolutionary potential of life-history traits is very low at northern compared to southern latitudes, but that changes in climate could alter this pattern.
|
|
| 3. |
- Sniegula, Szymon, et al.
(författare)
-
Size-mediated priority and temperature effects on intra-cohort competition and cannibalism in a damselfly
- 2019
-
Ingår i: Journal of Animal Ecology. - : WILEY. - 0021-8790 .- 1365-2656. ; 88:4, s. 637-648
-
Tidskriftsartikel (refereegranskat)abstract
- A shift in the relative arrival of offspring, for example a shift in hatching time, can affect competition at the intraspecific level through size-mediated priority effects, where the larger individuals gain more resources. These priority effects are likely to be affected by climate warming and the rate of intraspecific predation, that is cannibalism. In a laboratory experiment, we examined size-mediated priority effects in larvae of the univoltine damselfly, Lestes sponsa, at two different temperatures (21 and 23 degrees C). We created three size groups of larvae by manipulating hatching time: early hatched with a large size (extra-advanced), intermediate hatched with an intermediate size (advanced) and late hatched with a small size (non-advanced). Thereafter, we reared the larvae from these groups in non-mixed and mixed groups of 12 larvae. We found strong priority and temperature effects. First, extra-advanced larvae most often had higher survival, growth and development rates than non-advanced larvae in mixed groups, compared to groups that consisted of only extra-advanced larvae. Second, temperature increased growth and development rates and cannibalism. However, the strength of priority effects did not differ between the two experimental temperatures, because there was no statistical interaction between temperature and treatments. That is, the mixed and non-mixed groups of non-advanced, advanced and extra-advanced larvae showed the same relative change in life-history traits across the two temperatures. Non-advanced and advanced larvae had similar or higher growth rate and mass in mixed groups compared to non-mixed groups, suggesting that predation from advanced larvae in the mixed group released resources for the non-advanced and advanced larvae that survived despite cannibalism risk. Thus, a thinning effect occurred due to cannibalism caused by priority effects. The results suggest that a shift in the relative arrival of offspring can cause temperature-dependent priority effects, mediated through cannibalism, growth and development, which may change the size distribution and abundance of emerging aquatic insects.
|
|
| 4. |
- Johansson, Frank, et al.
(författare)
-
Scared fish get lazy, and lazy fish get fat
- 2009
-
Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 78:4, s. 772-777
-
Tidskriftsartikel (refereegranskat)abstract
- Many biological textbooks present predator-induced morphological changes in prey species as an example of an adaptive response, because the morphological change is associated with lower predation risk. Here we show that the adaptive morphological response observed in many systems may actually be an indirect effect of decreased activity which reduces the predation risk rather than a direct adaptive response. One of the classical examples comes from crucian carp, where the presence of pike leads to a deeper body. We manipulated pike cues (presence and absence) and water current (standing and running water) and found that both standing water and pike cues similarly and independently induced a deeper body. Since the presence of pike cues as well as standing water might be associated with low swimming activity, we suggest that the presence of pike causes a reduction in activity (antipredator behaviour). Reduced activity subsequently induces a deeper body, possibly because the energy saved is allocated to a higher growth rate. Our result suggests that even if morphological change is adaptive, it might be induced indirectly via activity. This important conceptual difference may be similar in many other systems.
|
|
