Hulton VanTassel Heather L, Bell Michael D, Rotenberry John, Johnson Robert, Allen Michael F
University of California Riverside CA USA.
Department of Biology University of California Riverside CA USA.
Ecol Evol. 2017 Oct 28;7(23):10326-10338. doi: 10.1002/ece3.3482. eCollection 2017 Dec.
Many species have already experienced distributional shifts due to changing environmental conditions, and analyzing past shifts can help us to understand the influence of environmental stressors on a species as well as to analyze the effectiveness of conservation strategies. We aimed to (1) quantify regional habitat associations of the California gnatcatcher (); (2) describe changes in environmental variables and gnatcatcher distributions through time; (3) identify environmental drivers associated with habitat suitability changes; and (4) relate habitat suitability changes through time to habitat conservation plans. Southern California's Western Riverside County (WRC), an approximately 4,675 km conservation planning area. We assessed environmental correlates of distributional shifts of the federally threatened California gnatcatcher (hereafter, gnatcatcher) using partitioned Mahalanobis niche modeling for three time periods: 1980-1997, 1998-2003, and 2004-2012, corresponding to distinct periods in habitat conservation planning. Highly suitable gnatcatcher habitat was consistently warmer and drier and occurred at a lower elevation than less suitable habitat and consistently had more CSS, less agriculture, and less chaparral. However, its relationship to development changed among periods, mainly due to the rapid change in this variable. Likewise, other aspects of highly suitable habitat changed among time periods, which became cooler and higher in elevation. The gnatcatcher lost 11.7% and 40.6% of highly suitable habitat within WRC between 1980-1997 to 1998-2003, and 1998-2003 to 2004-2012, respectively. Unprotected landscapes lost relatively more suitable habitat (-64.3%) than protected landscapes (30.5%). Over the past four decades, suitable habitat loss within WRC, especially between the second and third time periods, was associated with temperature-related factors coupled with landscape development across coastal sage scrub habitat; however, development appears to be driving change more rapidly than climate change. Our study demonstrates the importance of providing protected lands for potential suitable habitat in future scenarios.
由于环境条件的变化，许多物种已经经历了分布范围的转移，分析过去的转移情况有助于我们了解环境压力源对一个物种的影响，以及分析保护策略的有效性。我们的目标是：（1）量化加州食蜂鸟的区域栖息地关联；（2）描述环境变量和食蜂鸟分布随时间的变化；（3）识别与栖息地适宜性变化相关的环境驱动因素；（4）将栖息地适宜性随时间的变化与栖息地保护计划联系起来。南加州的西部河滨县（WRC），一个面积约4675平方公里的保护规划区域。我们使用分区马氏距离生态位模型，对三个时间段（1980 - 1997年、1998 - 2003年和2004 - 2012年）进行评估，这三个时间段对应着栖息地保护规划中的不同时期，以此来评估联邦濒危物种加州食蜂鸟（以下简称食蜂鸟）分布转移的环境相关因素。高度适宜食蜂鸟的栖息地一直更温暖、干燥，海拔比不太适宜的栖息地低，并且一直有更多的海岸鼠尾草群落、更少的农业用地和更少的丛林。然而，其与开发的关系在不同时期有所变化，主要是由于该变量的快速变化。同样，高度适宜栖息地的其他方面在不同时间段也发生了变化，变得更凉爽、海拔更高。在1980 - 1997年至1998 - 2003年以及1998 - 2003年至2004 - 2012年期间，食蜂鸟在WRC内分别失去了11.7%和40.6%的高度适宜栖息地。未受保护的景观比受保护的景观失去了相对更多的适宜栖息地（-64.3%对30.5%）。在过去的四十年里，WRC内适宜栖息地的丧失，特别是在第二个和第三个时间段之间，与温度相关因素以及沿海鼠尾草灌丛栖息地的景观开发有关；然而，开发似乎比气候变化更快地推动着变化。我们的研究表明，在未来情景中为潜在的适宜栖息地提供保护地的重要性。
