| Přispěvatelé: |
Radojčić Redovniković, Ivana, Radošević, Kristina, Jakovljević, Tamara, Stojaković, Renata, Gaurina Srček, Višnja, Erdec Hendrih, Dina |
| Popis: |
The European field elm (Ulmus minor Mill. sensu latissimo) is an important forest tree species, distributed mainly across southern Europe, where it grows as a common member of lowland pedunculate oak forests. Supplementary to the fact that it has been highly valued for its durable and resistant wood, use of its leaves and fruits as a cattle fodder and even for human nutrition has also been documented. Recently, U. minor s.l. populations were severely affected by numerous negative impacts that resulted in reduction of species adaptation potential. Flooding mitigation activities, disturbance of moisture regimes and modification of soil properties had profoundly adverse effects on ecological stability of floodplain forest sites. Moreover, devastating consequences of Dutch elm disease pandemics are evident through strikingly small number of the adult trees remaining in the field. Acknowledging that U. minor s.l. is generally sexual species with significant vegetative reproduction potential, decrease in the number of fructificating trees enabled change in reproduction system prioritizing from generative to vegetative way of spread. Prevalence of asexual way of reproduction is higher in populations hardly hit by DED phytopathogen, which are, due to higher incidence of disease vectors - elm bark beetles, mostly found in continental rather than in Mediterranean stands. The aim of this study was to reveal fruit outline shape variability in natural populations of U. minor s.l. from continental part of Croatia using elliptic Fourier descriptors. Solely simmetrycal shape variability elements of total 1000 fruit outlines were subjected to consecutive shape analyses. Matrix of Fourier coefficients was generated upon 20 harmonics and each outline was defined by 77 elliptic Forier coefficients. We found geometric morphometrics to be exceptionally applicable tool in expressing trends of morphological variation of elm fruit shapes. By applying Principal Component Analysis, three shape variables were obtained from the variance- covariance matrix. Proportional explained variance for the first, the second and the third principal component was 75, 3% ; 13, 1% and 4, 6% respectively. Analysis of variance, performed on PC scores, showed that all trees within populations differed significantly for every principal component inspected. Separation between four populations on the basis of the first principal component was corroborated. Likewise, significant deviation between three population pairs for the second principal component was also established. Nothwithstanding the fact capacity for sexual reproduction in elms due to DED is constantly decreasing, in this research we report high variability of fruit shapes in U. minor s.l. natural populations. |
