Ecosystem engineers alter the evolution of seed size by impacting fertility and the understory light environment

The extinction of the dinosaurs and later, the Pleistocene Megafauna, has been hypothesized to have created a darker forest subcanopy benefiting large-seeded plants. Larger seeds and their fruit, in turn, opened a dietary niche space for animals thus strongly shaping the ecology of the Cenozoic, including our fruit-eating primate ancestors. In this paper, we develop a mechanistic model where we replicate the conditions of tropical forests of the early Paleocene, with small animal body and small seed size, and the Holocene, with small animal body and large seed size.  We first calibrate light levels in our model using stable carbon isotope ratios from fossil leaves and estimate a decrease of understory light of ~90 µmol m-2 s-1 (a 19% decrease) from the Cretaceous to the Paleocene. Our model predicts a rapid increase in seed size during the Paleocene that eventually plateaued or declined slightly. Specifically, we find a dynamic feedback where increased animal sizes opened the under..., Model: To understand the long-term interactions between angiosperm seed size, animal size and the understory light environment, we created an individual based model using Matlab (Mathworks) with a grid size of 50 by 50 cells (also tested at 100 by 100). Each grid cell was assigned an initial animal bodyweight of 1kg and a seed size of 0.038g to simulate the small seeds and animals present in the aftermath of the dinosaur extinction event (Eriksson, 2016; Smith et al., 2010). We focus on angiosperm not gymnosperm seeds because the fruit surrounding angiosperm seeds will attract dispersers.  At each timestep, animal/seed mass is assigned based on randomly choosing a value within a distribution with a mean based on the animal/seed size from the prior timestep and a normally distributed standard deviation of 2/3 for plants/animals (also as 1% percent of body weight in a sensitivity study) with lower mass truncated at 0.038g for seeds and 0.03kg for animals (but no upper threshold). Tre..., , # Ecosystem engineers alter the evolution of seed size by impacting fertility and the understory light environment

[https://doi.org/10.5061/dryad.931zcrjw4](https://doi.org/10.5061/dryad.931zcrjw4)

## Description of the data and file structure

We use isotopic data from Graham et al 2019 and from Ehleringer et al 1986 to predict understory light differences.  We used data from Baraloto et al 2005 to establish relationships between seed size, height and survivability under different light conditions.  We use results from Faucet et al 2017 to predict vertical light profiles along a disturbance gradient and results from Montgomery 2004 to predict light profiles in the bottom meter of the canopy.  We use data from COALQUAL (CQ20166334750) (Palmer et al., 2015) to show chemical differences between time periods following the methodology from Doughty 2017 (Doughty, 2017).

### Files and variables

#### File: all\_paleo\_data.mat

**Description:** Data from various papers ...

恐龙的灭绝以及随后更新世巨型动物群（Pleistocene Megafauna）的消失，被假设为创造了更阴暗的林下冠层（subcanopy），从而有利于大种子植物的生存。反过来，更大的种子及其果实为动物开辟了饮食生态位空间，进而深刻塑造了新生代（Cenozoic）的生态系统，包括我们以果实为食的灵长类祖先。在本文中，我们开发了一个机制模型（mechanistic model），用以复现古新世（Paleocene）早期热带森林（动物体型小、种子尺寸小）和全新世（Holocene）热带森林（动物体型小、种子尺寸大）的条件。我们首先利用化石叶片的稳定碳同位素比值（stable carbon isotope ratios）校准模型中的光照水平，并估算出从白垩纪（Cretaceous）到古新世期间林下光照减少了约90 µmol m⁻² s⁻¹（下降19%）。我们的模型预测，古新世期间种子尺寸会快速增加，最终趋于平稳或略有下降。具体而言，我们发现一种动态反馈机制：动物体型增大打开了林下...

# 生态系统工程师通过影响繁殖力和林下冠层光环境改变种子大小的演化

[https://doi.org/10.5061/dryad.931zcrjw4](https://doi.org/10.5061/dryad.931zcrjw4)

## 数据与文件结构描述

我们使用Graham等人2019年以及Ehleringer等人1986年的同位素数据预测林下光照差异。我们利用Baraloto等人2005年的数据建立种子大小、高度与不同光环境下存活率之间的关系。我们采用Faucet等人2017年的结果预测干扰梯度（disturbance gradient）上的垂直光剖面（vertical light profiles），并利用Montgomery 2004年的结果预测冠层底部一米处的光剖面。我们使用COALQUAL（CQ20166334750）（Palmer等人，2015）的数据，遵循Doughty 2017年的方法（Doughty, 2017）展示不同时期的化学差异。

### 文件与变量

#### 文件：all_paleo_data.mat

**描述：** 来自多篇论文的数据...