Succession and seasonality drive tropical butterfly assembly after an extreme hurricane

We monitored butterfly communities in two Puerto Rican forests differing in structure to assess butterfly diversity, abundances, and community-level wing traits (size and color) over one year, beginning six months after Hurricane Maria. This dataset includes monthly species counts (abundances), species mean wing trait values, and site level characteristics including abiotic (temperature, humidity, canopy openness) and derived community-weighted mean metrics (i.e., functional diversity, and community-weighted mean trait values). Monthly sampling revealed no significant relationships between abundances and canopy openness or humidity; instead, species abundances fluctuated seasonally and were non-linearly correlated with temperature. In contrast, wing size and color were linearly correlated with changes in abiotic conditions, indicating that the hurricane differentially impacted larger-sized and functionally rare species. Specifically, wings were larger in cooler and more open conditions. Wing saturation was positively correlated with lower temperatures and negatively correlated with humidity. Our results suggest that, first, a functional approach may provide better insight into the factors mediating species responses to disturbances and, second, disentangling abundance seasonality from successional processes necessitates long-term monitoring.

Methods
We monitored butterfly populations in two forests located in Puerto Rico’s Cordillera Central: Bosque del Pueblo and Bosque La Olimpia using nets, fruit bait traps, and visual counts. For visual counts, we performed standardized transect walks along a 2 km route, with approximately seven person-hours dedicated to sampling per month per site over one year.

We collected three individuals per species, usually one female, one male (when sex could be differentiated in the field), and an additional individual, to prepare as voucher specimens. All specimens were deposited at the Museo de Zoologia at the University of Puerto Rico-Rio Piedras (museum code: UPRRP). Furthermore, we measured the canopy cover using a fish-eye lens (ECO-FUSED, U.S.) attached to a smartphone and analyzed images using the Gap Light Analyzer application which calculates the percentage of occupied pixels and thus canopy cover. We also measured temperature and humidity using data loggers.

We photographed all voucher specimens using standardized protocols and used the resulting images to calculate wing size using image analysis software (ImageJ/FIJI). We measured two forewing traits on all specimens: wing length, calculated as the length in centimeters of the longest axis from the point of wing attachment at the thorax (disc cell) to the distal tip (R4 vein), and wing width, calculated as the width in centimeters of the longest line (R2 vein) that could be drawn perpendicular to the A2 anal vein. We also measured wing color using image analysis software on a 1 cm2 square area near the thorax, avoiding veins and regions with damaged or missing scales. We converted the raw RGB (red, green, blue) digital images to HSB images (hue, saturation, brightness, and intensity color space; Schindelin et al. 2012). 

Next, to analyze functional community structure through time, we calculated community-weighted means (CWMs) and functional diversity metrics based on species composition, trait values, and abundances at each site at each sampling occurrence.

本研究于飓风玛丽亚（Hurricane Maria）过境六个月后启动，针对结构存在差异的两处波多黎各森林开展为期一年的蝴蝶群落监测，以评估蝴蝶多样性、种群丰度以及群落水平的翅部性状（翅大小与翅色）。本数据集包含月度物种计数（丰度）、物种平均翅部性状值，以及样地水平特征：非生物因子（温度、湿度、冠层开度），以及衍生的群落加权平均指标（即功能多样性与群落加权平均性状值）。
月度采样结果显示，种群丰度与冠层开度、湿度之间无显著相关性；反之，物种丰度呈现季节性波动，且与温度呈非线性相关。与之相对，翅大小与翅色则与非生物因子变化呈线性相关，表明该飓风对体型较大以及功能上稀有的物种产生了差异化影响。具体而言，在温度更低、冠层更开阔的生境中，蝴蝶翅更大。翅饱和度与较低温度呈正相关，与湿度呈负相关。本研究结果表明：其一，功能性状分析方法可更深入地解析调控物种对干扰响应的关键因子；其二，若要区分丰度季节性波动与群落演替过程，则需开展长期监测工作。

## 研究方法
我们在波多黎各中部山脉（Cordillera Central）的两处森林——博斯克德尔普韦布洛（Bosque del Pueblo）与博斯克拉奥利匹亚（Bosque La Olimpia）——利用捕虫网、果实诱饵诱捕器以及目视计数法开展蝴蝶种群监测。目视计数环节采用标准化样带行走法，沿2公里的样线开展采样，整个监测周期为一年，每个样地每月投入约7人·小时用于采样工作。

我们为每个物种采集3个个体：通常为1只雌性、1只雄性（若野外可区分性别），以及额外1只个体，用于制作凭证标本。所有标本均存放于波多黎各大学里约皮埃德拉斯分校动物学博物馆（Museo de Zoologia, University of Puerto Rico-Rio Piedras；馆藏编号：UPRRP）。此外，我们使用搭载于智能手机的鱼眼镜头（ECO-FUSED，美国）拍摄冠层照片，并利用Gap Light Analyzer软件分析图像，该软件可通过统计像素占比计算冠层覆盖率。我们还利用数据记录器测定了温度与湿度。

我们按照标准化流程对所有凭证标本进行拍照，并利用图像分析软件（ImageJ/FIJI）基于照片计算翅大小。我们对所有标本的两个前翅性状进行了测定：翅长，即从胸部着翅点（盘室，disc cell）至翅端（R4脉，R4 vein）的最长轴线长度（单位：厘米）；翅宽，即垂直于A2臀脉（A2 anal vein）所能绘制的最长线段（R2脉，R2 vein）的宽度（单位：厘米）。我们还利用图像分析软件，在标本胸部附近的1平方厘米方形区域内测定翅色，测定时避开翅脉以及鳞片受损或缺失的区域。我们将原始RGB（红、绿、蓝）数字图像转换为HSB图像（色相、饱和度、明度与强度色彩空间；Schindelin等，2012）。

随后，为分析群落功能结构随时间的变化，我们基于各采样节点的物种组成、性状值与种群丰度，计算了群落加权平均性状值（CWMs）与功能多样性指标。