Large Contiguous Patches Research Articles

Long-Term Persistence of Song Dialects in the Mountain White-Crowned Sparrow

This study examined the persistence of local song dialects of Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) at several locations in the Sierra Nevada Mountains of California. At two of these locations, where sparrows were numerous and occupied large contiguous habitat patches, song structure remained highly consistent over a 26-year period (1970-1996). Small but significant alterations in some aspects of the component syllables appeared to result from accumulation of slight copying errors. The frequency and duration of the introductory whistle changed little while the trill and complex syllables changed significantly. Dialects at these two locations were unaffected by extinction of syllables or invasion by foreign syllables. In contrast, songs recorded from two other areas (fragmented habitat and small populations) exhibited dramatic qualitative changes in overall structure and component syllables. These changes resulted both from loss of syllables and appearance of new syllables evidently introduced from nearby areas. These findings suggest that evolution of this culturally transmitted trait (song) proceeds more rapidly in smaller populations occupying structurally fragmented habitats than in larger populations occupying large contiguous habitat patches.

Cloned interstitial stem cells grow as contiguous patches in hydra

The migration of interstitial cells was analyzed during the growth of stem cell clones in vivo. The spatial distribution of cloned cells was analyzed at a time by which extensive migration of interstitial cells could have occurred. All interstitial cell clones were found to form large contiguous patches of cells. The results indicate that there is little migration of large interstitial cells in undisturbed tissue during normal growth. This finding is surprising since numerous grafting experiments have shown extensive migration of these cells. The implications of finding nonrandomly distributed stem cells are discussed.

Quantifying the distribution and abundance of an animals resource using aerial photography.

Infra-red aerial photography was used on two occasions to map the abundance and dispersion of milkweeds (Asclepias spp.). The scale at which the aerial photographs could be interpreted showed that milkweeds occur in large contiguous areas or patches. These patches are abundant, the number in any size-class declining exponentially with increasing size. Analysis of the maps using various dispersion indices and spatial autocorrelation statistic showed that patches have a clumped dispersion. Large patches tend to be surrounded by smaller sized patches. The scales at which clumping occurred indicated a close association between milkweeds and the degree of disturbance of the 'natural' environment by human activities. The utility of resource mapping using aerial photography is demonstrated.